Fixed Mac OS X config header when compiling with -Wundef.

--HG--
branch : SDL-1.2
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/branches/SDL-1.2%402288

include/SDL_config_macosx.h

@@ -117,7 +117,7 @@
 
 /* Enable various video drivers */
 #define SDL_VIDEO_DRIVER_DUMMY	1
-#if TARGET_API_MAC_CARBON
+#if ((defined TARGET_API_MAC_CARBON) && (TARGET_API_MAC_CARBON))
 #define SDL_VIDEO_DRIVER_TOOLBOX	1
 #else
 #define SDL_VIDEO_DRIVER_QUARTZ	1