Avoid gcc parse errors on Win32. This is fine in general because gcc uses

the cdecl calling convention by default.

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%401026

include/begin_code.h

@@ -63,7 +63,7 @@
 
 /* By default SDL uses the C calling convention */
 #ifndef SDLCALL
-#ifdef WIN32
+#if defined(WIN32) && !defined(__GNUC__)
 #define SDLCALL __cdecl
 #else
 #define SDLCALL