Define __MINGW64_TOOLCHAIN__ and __MINGW32_TOOLCHAIN__ symbols.

__MINGW64_TOOLCHAIN__ macro is more readable and shorter than the standard
predefined __MINGW64_VERSION_MAJOR and __MINGW32_TOOLCHAIN__ is defined for
the symmetry and also because it will make many tests simpler as we often
need to test not so much for MinGW-w64 for its own sake but rather to disable
the workarounds for MinGW32 when using it.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74885 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/compiler.h

@@ -144,6 +144,28 @@
     #define wxCHECK_MINGW32_VERSION( major, minor ) \
  ( ( ( __MINGW32_MAJOR_VERSION > (major) ) \
       || ( __MINGW32_MAJOR_VERSION == (major) && __MINGW32_MINOR_VERSION >= (minor) ) ) )
+
+/*
+    MinGW-w64 project provides compilers for both Win32 and Win64 but only
+    defines the same __MINGW32__ symbol for the former as MinGW32 toolchain
+    which is quite different (notably doesn't provide many SDK headers that
+    MinGW-w64 does include). So we define a separate symbol which, unlike the
+    predefined __MINGW64__, can be used to detect this toolchain in both 32 and
+    64 bit builds.
+
+    And define __MINGW32_TOOLCHAIN__ for consistency and also because it's
+    convenient as we often want to have some workarounds only for the (old)
+    MinGW32 but not (newer) MinGW-w64, which still predefines __MINGW32__.
+ */
+#   ifdef __MINGW64_VERSION_MAJOR
+#       ifndef __MINGW64_TOOLCHAIN__
+#           define __MINGW64_TOOLCHAIN__
+#       endif
+#   else
+#       ifndef __MINGW32_TOOLCHAIN__
+#           define __MINGW32_TOOLCHAIN__
+#       endif
+#   endif
 #else
     #define wxCHECK_MINGW32_VERSION( major, minor ) (0)
 #endif