diff --git a/build-aux/m4/bitcoin_qt.m4 b/build-aux/m4/bitcoin_qt.m4
index 8f442430e7..f41508336c 100644
--- a/build-aux/m4/bitcoin_qt.m4
+++ b/build-aux/m4/bitcoin_qt.m4
@@ -5,8 +5,8 @@ dnl file COPYING or http://www.opensource.org/licenses/mit-license.php.
 dnl Helper for cases where a qt dependency is not met.
 dnl Output: If qt version is auto, set bitcoin_enable_qt to false. Else, exit.
 AC_DEFUN([BITCOIN_QT_FAIL],[
-  if test "x$bitcoin_qt_want_version" = "xauto" && test x$bitcoin_qt_force != xyes; then
-    if test x$bitcoin_enable_qt != xno; then
+  if test "x$bitcoin_qt_want_version" = xauto && test "x$bitcoin_qt_force" != xyes; then
+    if test "x$bitcoin_enable_qt" != xno; then
       AC_MSG_WARN([$1; bitcoin-qt frontend will not be built])
     fi
     bitcoin_enable_qt=no
@@ -17,7 +17,7 @@ AC_DEFUN([BITCOIN_QT_FAIL],[
 ])
 
 AC_DEFUN([BITCOIN_QT_CHECK],[
-  if test "x$bitcoin_enable_qt" != "xno" && test x$bitcoin_qt_want_version != xno; then
+  if test "x$bitcoin_enable_qt" != xno && test "x$bitcoin_qt_want_version" != xno; then
     true
     $1
   else
@@ -35,12 +35,12 @@ dnl Inputs: $4: If "yes", don't fail if $2 is not found.
 dnl Output: $1 is set to the path of $2 if found. $2 are searched in order.
 AC_DEFUN([BITCOIN_QT_PATH_PROGS],[
   BITCOIN_QT_CHECK([
-    if test "x$3" != "x"; then
+    if test "x$3" != x; then
       AC_PATH_PROGS($1,$2,,$3)
     else
       AC_PATH_PROGS($1,$2)
     fi
-    if test "x$$1" = "x" && test "x$4" != "xyes"; then
+    if test "x$$1" = x && test "x$4" != xyes; then
       BITCOIN_QT_FAIL([$1 not found])
     fi
   ])
@@ -57,7 +57,7 @@ AC_DEFUN([BITCOIN_QT_INIT],[
     [build bitcoin-qt GUI (default=auto, qt5 tried first)])],
     [
      bitcoin_qt_want_version=$withval
-     if test x$bitcoin_qt_want_version = xyes; then
+     if test "x$bitcoin_qt_want_version" = xyes; then
        bitcoin_qt_force=yes
        bitcoin_qt_want_version=auto
      fi
@@ -89,11 +89,11 @@ dnl Outputs: bitcoin_enable_qt, bitcoin_enable_qt_dbus, bitcoin_enable_qt_test
 AC_DEFUN([BITCOIN_QT_CONFIGURE],[
   use_pkgconfig=$1
 
-  if test x$use_pkgconfig = x; then
+  if test "x$use_pkgconfig" = x; then
     use_pkgconfig=yes
   fi
 
-  if test x$use_pkgconfig = xyes; then
+  if test "x$use_pkgconfig" = xyes; then
     BITCOIN_QT_CHECK([_BITCOIN_QT_FIND_LIBS_WITH_PKGCONFIG([$2])])
   else
     BITCOIN_QT_CHECK([_BITCOIN_QT_FIND_LIBS_WITHOUT_PKGCONFIG])
@@ -113,9 +113,9 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
   TEMP_CXXFLAGS=$CXXFLAGS
   CPPFLAGS="$QT_INCLUDES $CPPFLAGS"
   CXXFLAGS="$PIC_FLAGS $CXXFLAGS"
-  if test x$bitcoin_qt_got_major_vers = x5; then
+  if test "x$bitcoin_qt_got_major_vers" = x5; then
     _BITCOIN_QT_IS_STATIC
-    if test x$bitcoin_cv_static_qt = xyes; then
+    if test "x$bitcoin_cv_static_qt" = xyes; then
       _BITCOIN_QT_FIND_STATIC_PLUGINS
       AC_DEFINE(QT_STATICPLUGIN, 1, [Define this symbol if qt plugins are static])
       AC_CACHE_CHECK(for Qt < 5.4, bitcoin_cv_need_acc_widget,[
@@ -133,25 +133,25 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
         [bitcoin_cv_need_acc_widget=yes],
         [bitcoin_cv_need_acc_widget=no])
       ])
-      if test "x$bitcoin_cv_need_acc_widget" = "xyes"; then
+      if test "x$bitcoin_cv_need_acc_widget" = xyes; then
         _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(AccessibleFactory)], [-lqtaccessiblewidgets])
       fi
       _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QMinimalIntegrationPlugin)],[-lqminimal])
       AC_DEFINE(QT_QPA_PLATFORM_MINIMAL, 1, [Define this symbol if the minimal qt platform exists])
-      if test x$TARGET_OS = xwindows; then
+      if test "x$TARGET_OS" = xwindows; then
         _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QWindowsIntegrationPlugin)],[-lqwindows])
         AC_DEFINE(QT_QPA_PLATFORM_WINDOWS, 1, [Define this symbol if the qt platform is windows])
-      elif test x$TARGET_OS = xlinux; then
+      elif test "x$TARGET_OS" = xlinux; then
         _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QXcbIntegrationPlugin)],[-lqxcb -lxcb-static])
         AC_DEFINE(QT_QPA_PLATFORM_XCB, 1, [Define this symbol if the qt platform is xcb])
-      elif test x$TARGET_OS = xdarwin; then
+      elif test "x$TARGET_OS" = xdarwin; then
         AX_CHECK_LINK_FLAG([[-framework IOKit]],[QT_LIBS="$QT_LIBS -framework IOKit"],[AC_MSG_ERROR(could not iokit framework)])
         _BITCOIN_QT_CHECK_STATIC_PLUGINS([Q_IMPORT_PLUGIN(QCocoaIntegrationPlugin)],[-lqcocoa])
         AC_DEFINE(QT_QPA_PLATFORM_COCOA, 1, [Define this symbol if the qt platform is cocoa])
       fi
     fi
   else
-    if test x$TARGET_OS = xwindows; then
+    if test "x$TARGET_OS" = xwindows; then
       AC_DEFINE(QT_STATICPLUGIN, 1, [Define this symbol if qt plugins are static])
       _BITCOIN_QT_CHECK_STATIC_PLUGINS([
          Q_IMPORT_PLUGIN(qcncodecs)
@@ -166,13 +166,13 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
   CXXFLAGS=$TEMP_CXXFLAGS
   ])
 
-  if test x$use_pkgconfig$qt_bin_path = xyes; then
-    if test x$bitcoin_qt_got_major_vers = x5; then
+  if test "x$use_pkgconfig$qt_bin_path" = xyes; then
+    if test "x$bitcoin_qt_got_major_vers" = x5; then
       qt_bin_path="`$PKG_CONFIG --variable=host_bins Qt5Core 2>/dev/null`"
     fi
   fi
 
-  if test x$use_hardening != xno; then
+  if test "x$use_hardening" != xno; then
     BITCOIN_QT_CHECK([
     AC_MSG_CHECKING(whether -fPIE can be used with this Qt config)
     TEMP_CPPFLAGS=$CPPFLAGS
@@ -246,17 +246,17 @@ AC_DEFUN([BITCOIN_QT_CONFIGURE],[
   BITCOIN_QT_CHECK([
     bitcoin_enable_qt=yes
     bitcoin_enable_qt_test=yes
-    if test x$have_qt_test = xno; then
+    if test "x$have_qt_test" = xno; then
       bitcoin_enable_qt_test=no
     fi
     bitcoin_enable_qt_dbus=no
-    if test x$use_dbus != xno && test x$have_qt_dbus = xyes; then
+    if test "x$use_dbus" != xno && test "x$have_qt_dbus" = xyes; then
       bitcoin_enable_qt_dbus=yes
     fi
-    if test x$use_dbus = xyes && test x$have_qt_dbus = xno; then
+    if test "x$use_dbus" = xyes && test "x$have_qt_dbus" = xno; then
       AC_MSG_ERROR([libQtDBus not found. Install libQtDBus or remove --with-qtdbus.])
     fi
-    if test x$LUPDATE = x; then
+    if test "x$LUPDATE" = x; then
       AC_MSG_WARN([lupdate is required to update qt translations])
     fi
   ],[
@@ -321,7 +321,7 @@ AC_DEFUN([_BITCOIN_QT_IS_STATIC],[
     [bitcoin_cv_static_qt=yes],
     [bitcoin_cv_static_qt=no])
   ])
-  if test x$bitcoin_cv_static_qt = xyes; then
+  if test "x$bitcoin_cv_static_qt" = xyes; then
     AC_DEFINE(QT_STATICPLUGIN, 1, [Define this symbol for static Qt plugins])
   fi
 ])
@@ -350,28 +350,28 @@ dnl Inputs: bitcoin_qt_got_major_vers. 4 or 5.
 dnl Inputs: qt_plugin_path. optional.
 dnl Outputs: QT_LIBS is appended
 AC_DEFUN([_BITCOIN_QT_FIND_STATIC_PLUGINS],[
-  if test x$bitcoin_qt_got_major_vers = x5; then
-      if test x$qt_plugin_path != x; then
+  if test "x$bitcoin_qt_got_major_vers" = x5; then
+      if test "x$qt_plugin_path" != x; then
         QT_LIBS="$QT_LIBS -L$qt_plugin_path/platforms"
         if test -d "$qt_plugin_path/accessible"; then
           QT_LIBS="$QT_LIBS -L$qt_plugin_path/accessible"
         fi
       fi
-     if test x$use_pkgconfig = xyes; then
+     if test "x$use_pkgconfig" = xyes; then
      : dnl
      m4_ifdef([PKG_CHECK_MODULES],[
        PKG_CHECK_MODULES([QTPLATFORM], [Qt5PlatformSupport], [QT_LIBS="$QTPLATFORM_LIBS $QT_LIBS"])
-       if test x$TARGET_OS = xlinux; then
+       if test "x$TARGET_OS" = xlinux; then
          PKG_CHECK_MODULES([X11XCB], [x11-xcb], [QT_LIBS="$X11XCB_LIBS $QT_LIBS"])
          if ${PKG_CONFIG} --exists "Qt5Core >= 5.5" 2>/dev/null; then
            PKG_CHECK_MODULES([QTXCBQPA], [Qt5XcbQpa], [QT_LIBS="$QTXCBQPA_LIBS $QT_LIBS"])
          fi
-       elif test x$TARGET_OS = xdarwin; then
+       elif test "x$TARGET_OS" = xdarwin; then
          PKG_CHECK_MODULES([QTPRINT], [Qt5PrintSupport], [QT_LIBS="$QTPRINT_LIBS $QT_LIBS"])
        fi
      ])
      else
-       if test x$TARGET_OS = xwindows; then
+       if test "x$TARGET_OS" = xwindows; then
          AC_CACHE_CHECK(for Qt >= 5.6, bitcoin_cv_need_platformsupport,[
            AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
                #include <QtCore/qconfig.h>
@@ -387,13 +387,13 @@ AC_DEFUN([_BITCOIN_QT_FIND_STATIC_PLUGINS],[
            [bitcoin_cv_need_platformsupport=yes],
            [bitcoin_cv_need_platformsupport=no])
          ])
-         if test x$bitcoin_cv_need_platformsupport = xyes; then
+         if test "x$bitcoin_cv_need_platformsupport" = xyes; then
            BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}PlatformSupport],[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}PlatformSupport not found)))
          fi
        fi
      fi
   else
-    if test x$qt_plugin_path != x; then
+    if test "x$qt_plugin_path" != x; then
       QT_LIBS="$QT_LIBS -L$qt_plugin_path/accessible"
       QT_LIBS="$QT_LIBS -L$qt_plugin_path/codecs"
     fi
@@ -411,10 +411,10 @@ dnl Outputs: have_qt_test and have_qt_dbus are set (if applicable) to yes|no.
 AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITH_PKGCONFIG],[
   m4_ifdef([PKG_CHECK_MODULES],[
   auto_priority_version=$1
-  if test x$auto_priority_version = x; then
+  if test "x$auto_priority_version" = x; then
     auto_priority_version=qt5
   fi
-    if test x$bitcoin_qt_want_version = xqt5 ||  ( test x$bitcoin_qt_want_version = xauto && test x$auto_priority_version = xqt5 ); then
+    if test "x$bitcoin_qt_want_version" = xqt5 ||  ( test "x$bitcoin_qt_want_version" = xauto && test "x$auto_priority_version" = xqt5 ); then
       QT_LIB_PREFIX=Qt5
       bitcoin_qt_got_major_vers=5
     else
@@ -424,28 +424,28 @@ AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITH_PKGCONFIG],[
     qt5_modules="Qt5Core Qt5Gui Qt5Network Qt5Widgets"
     qt4_modules="QtCore QtGui QtNetwork"
     BITCOIN_QT_CHECK([
-      if test x$bitcoin_qt_want_version = xqt5 || ( test x$bitcoin_qt_want_version = xauto && test x$auto_priority_version = xqt5 ); then
+      if test "x$bitcoin_qt_want_version" = xqt5 || ( test "x$bitcoin_qt_want_version" = xauto && test "x$auto_priority_version" = xqt5 ); then
         PKG_CHECK_MODULES([QT5], [$qt5_modules], [QT_INCLUDES="$QT5_CFLAGS"; QT_LIBS="$QT5_LIBS" have_qt=yes],[have_qt=no])
-      elif test x$bitcoin_qt_want_version = xqt4 || ( test x$bitcoin_qt_want_version = xauto && test x$auto_priority_version = xqt4 ); then
+      elif test "x$bitcoin_qt_want_version" = xqt4 || ( test "x$bitcoin_qt_want_version" = xauto && test "x$auto_priority_version" = xqt4 ); then
         PKG_CHECK_MODULES([QT4], [$qt4_modules], [QT_INCLUDES="$QT4_CFLAGS"; QT_LIBS="$QT4_LIBS" ; have_qt=yes], [have_qt=no])
       fi
 
       dnl qt version is set to 'auto' and the preferred version wasn't found. Now try the other.
-      if test x$have_qt = xno && test x$bitcoin_qt_want_version = xauto; then
-        if test x$auto_priority_version = xqt5; then
+      if test "x$have_qt" = xno && test "x$bitcoin_qt_want_version" = xauto; then
+        if test "x$auto_priority_version" = xqt5; then
           PKG_CHECK_MODULES([QT4], [$qt4_modules], [QT_INCLUDES="$QT4_CFLAGS"; QT_LIBS="$QT4_LIBS" ; have_qt=yes; QT_LIB_PREFIX=Qt; bitcoin_qt_got_major_vers=4], [have_qt=no])
         else
           PKG_CHECK_MODULES([QT5], [$qt5_modules], [QT_INCLUDES="$QT5_CFLAGS"; QT_LIBS="$QT5_LIBS" ; have_qt=yes; QT_LIB_PREFIX=Qt5; bitcoin_qt_got_major_vers=5], [have_qt=no])
         fi
       fi
-      if test x$have_qt != xyes; then
+      if test "x$have_qt" != xyes; then
         have_qt=no
         BITCOIN_QT_FAIL([Qt dependencies not found])
       fi
     ])
     BITCOIN_QT_CHECK([
       PKG_CHECK_MODULES([QT_TEST], [${QT_LIB_PREFIX}Test], [QT_TEST_INCLUDES="$QT_TEST_CFLAGS"; have_qt_test=yes], [have_qt_test=no])
-      if test x$use_dbus != xno; then
+      if test "x$use_dbus" != xno; then
         PKG_CHECK_MODULES([QT_DBUS], [${QT_LIB_PREFIX}DBus], [QT_DBUS_INCLUDES="$QT_DBUS_CFLAGS"; have_qt_dbus=yes], [have_qt_dbus=no])
       fi
     ])
@@ -466,7 +466,7 @@ AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITHOUT_PKGCONFIG],[
   CXXFLAGS="$PIC_FLAGS $CXXFLAGS"
   TEMP_LIBS="$LIBS"
   BITCOIN_QT_CHECK([
-    if test x$qt_include_path != x; then
+    if test "x$qt_include_path" != x; then
       QT_INCLUDES="-I$qt_include_path -I$qt_include_path/QtCore -I$qt_include_path/QtGui -I$qt_include_path/QtWidgets -I$qt_include_path/QtNetwork -I$qt_include_path/QtTest -I$qt_include_path/QtDBus"
       CPPFLAGS="$QT_INCLUDES $CPPFLAGS"
     fi
@@ -477,10 +477,10 @@ AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITHOUT_PKGCONFIG],[
   BITCOIN_QT_CHECK([AC_CHECK_HEADER([QLocalSocket],, BITCOIN_QT_FAIL(QtNetwork headers missing))])
 
   BITCOIN_QT_CHECK([
-    if test x$bitcoin_qt_want_version = xauto; then
+    if test "x$bitcoin_qt_want_version" = xauto; then
       _BITCOIN_QT_CHECK_QT5
     fi
-    if test x$bitcoin_cv_qt5 = xyes || test x$bitcoin_qt_want_version = xqt5; then
+    if test "x$bitcoin_cv_qt5" = xyes || test "x$bitcoin_qt_want_version" = xqt5; then
       QT_LIB_PREFIX=Qt5
       bitcoin_qt_got_major_vers=5
     else
@@ -491,11 +491,11 @@ AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITHOUT_PKGCONFIG],[
 
   BITCOIN_QT_CHECK([
     LIBS=
-    if test x$qt_lib_path != x; then
+    if test "x$qt_lib_path" != x; then
       LIBS="$LIBS -L$qt_lib_path"
     fi
 
-    if test x$TARGET_OS = xwindows; then
+    if test "x$TARGET_OS" = xwindows; then
       AC_CHECK_LIB([imm32],      [main],, BITCOIN_QT_FAIL(libimm32 not found))
     fi
   ])
@@ -508,7 +508,7 @@ AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITHOUT_PKGCONFIG],[
   BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}Core]   ,[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}Core not found)))
   BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}Gui]    ,[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}Gui not found)))
   BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}Network],[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}Network not found)))
-  if test x$bitcoin_qt_got_major_vers = x5; then
+  if test "x$bitcoin_qt_got_major_vers" = x5; then
     BITCOIN_QT_CHECK(AC_CHECK_LIB([${QT_LIB_PREFIX}Widgets],[main],,BITCOIN_QT_FAIL(lib${QT_LIB_PREFIX}Widgets not found)))
   fi
   QT_LIBS="$LIBS"
@@ -516,15 +516,15 @@ AC_DEFUN([_BITCOIN_QT_FIND_LIBS_WITHOUT_PKGCONFIG],[
 
   BITCOIN_QT_CHECK([
     LIBS=
-    if test x$qt_lib_path != x; then
+    if test "x$qt_lib_path" != x; then
       LIBS="-L$qt_lib_path"
     fi
     AC_CHECK_LIB([${QT_LIB_PREFIX}Test],      [main],, have_qt_test=no)
     AC_CHECK_HEADER([QTest],, have_qt_test=no)
     QT_TEST_LIBS="$LIBS"
-    if test x$use_dbus != xno; then
+    if test "x$use_dbus" != xno; then
       LIBS=
-      if test x$qt_lib_path != x; then
+      if test "x$qt_lib_path" != x; then
         LIBS="-L$qt_lib_path"
       fi
       AC_CHECK_LIB([${QT_LIB_PREFIX}DBus],      [main],, have_qt_dbus=no)