SDL_pixels.h needs SDL_stdinc.h for SDL_FOURCC #define (thanks, Dmitry!).

Fixes Bugzilla #2384.

include/SDL_pixels.h

@@ -28,6 +28,8 @@
 #ifndef _SDL_pixels_h
 #define _SDL_pixels_h
 
+#include "SDL_stdinc.h"
+
 #include "begin_code.h"
 /* Set up for C function definitions, even when using C++ */
 #ifdef __cplusplus