Organise Linux build instructions to be categorised by distro

doc/build-unix.md

@@ -62,8 +62,13 @@ tuned to conserve memory with additional CXXFLAGS:
 
     ./configure CXXFLAGS="--param ggc-min-expand=1 --param ggc-min-heapsize=32768"
 
-Dependency Build Instructions: Ubuntu & Debian
-----------------------------------------------
+
+## Linux Distribution Specific Instructions
+
+### Ubuntu & Debian
+
+#### Dependency Build Instructions
+
 Build requirements:
 
     sudo apt-get install build-essential libtool autotools-dev automake pkg-config libssl-dev libevent-dev bsdmainutils python3
@@ -105,8 +110,7 @@ ZMQ dependencies (provides ZMQ API 4.x):
 
     sudo apt-get install libzmq3-dev
 
-Dependencies for the GUI: Ubuntu & Debian
------------------------------------------
+#### Dependencies for the GUI
 
 If you want to build Bitcoin-Qt, make sure that the required packages for Qt development
 are installed. Either Qt 5 or Qt 4 are necessary to build the GUI.
@@ -128,8 +132,11 @@ libqrencode (optional) can be installed with:
 Once these are installed, they will be found by configure and a bitcoin-qt executable will be
 built by default.
 
-Dependency Build Instructions: Fedora
--------------------------------------
+
+### Fedora
+
+#### Dependency Build Instructions
+
 Build requirements:
 
     sudo dnf install gcc-c++ libtool make autoconf automake openssl-devel libevent-devel boost-devel libdb4-devel libdb4-cxx-devel python3