cmake: set minimum version to 3.5

Fix generated pkg-config files, see
https://github.com/libevent/libevent/pull/1165.

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,7 +19,7 @@
 #       start libevent.sln
 #
 
-cmake_minimum_required(VERSION 3.1 FATAL_ERROR)
+cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
 
 if (POLICY CMP0054)
     cmake_policy(SET CMP0054 NEW)
diff --git a/cmake/AddEventLibrary.cmake b/cmake/AddEventLibrary.cmake
index 04f5837e..d8ea42c4 100644
--- a/cmake/AddEventLibrary.cmake
+++ b/cmake/AddEventLibrary.cmake
@@ -20,12 +20,12 @@ macro(generate_pkgconfig LIB_NAME)
 
     set(LIBS         "")
     foreach (LIB ${LIB_PLATFORM})
-        set(LIBS "${LIBS} -L${LIB}")
+        set(LIBS "${LIBS} -l${LIB}")
     endforeach()
 
     set(OPENSSL_LIBS "")
     foreach(LIB ${OPENSSL_LIBRARIES})
-        set(OPENSSL_LIBS "${OPENSSL_LIBS} -L${LIB}")
+        set(OPENSSL_LIBS "${OPENSSL_LIBS} -l${LIB}")
     endforeach()
 
     configure_file("lib${LIB_NAME}.pc.in" "lib${LIB_NAME}.pc" @ONLY)