Help: Add links to variables

Help/prop_tgt/WIN32_EXECUTABLE.rst

@@ -5,8 +5,8 @@ Build an executable with a WinMain entry point on windows.
 
 When this property is set to true the executable when linked on
 Windows will be created with a WinMain() entry point instead of just
-main().  This makes it a GUI executable instead of a console
-application.  See the CMAKE_MFC_FLAG variable documentation to
+main().  This makes it a GUI executable instead of a console application.
+See the :variable:`CMAKE_MFC_FLAG` variable documentation to
 configure use of MFC for WinMain executables.  This property is
-initialized by the value of the variable CMAKE_WIN32_EXECUTABLE if it
-is set when a target is created.
+initialized by the value of the :variable:`CMAKE_WIN32_EXECUTABLE`
+variable if it is set when a target is created.