WIN32 is no longer defined on Windows builds

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%401540

src/video/SDL_sysvideo.h

@@ -184,7 +184,7 @@ struct SDL_VideoDevice {
 
   	/* OpenGL functions for SDL_OPENGLBLIT */
 #if SDL_VIDEO_OPENGL
-#ifndef WIN32
+#if !defined(__WIN32__)
 #define WINAPI
 #endif
 #define SDL_PROC(ret,func,params) ret (WINAPI *func) params;