Add SDL_guid.h to the global SDL header

include/SDL.h

@@ -41,6 +41,7 @@
 #include "SDL_events.h"
 #include "SDL_filesystem.h"
 #include "SDL_gamecontroller.h"
+#include "SDL_guid.h"
 #include "SDL_haptic.h"
 #include "SDL_hidapi.h"
 #include "SDL_hints.h"