Fixed Mac and Linux builds

src/dynapi/SDL_dynapi_procs.h

@@ -624,4 +624,6 @@ SDL_DYNAPI_PROC(int,SDL_QueueAudio,(SDL_AudioDeviceID a, const void *b, Uint32 c
 SDL_DYNAPI_PROC(Uint32,SDL_GetQueuedAudioSize,(SDL_AudioDeviceID a),(a),return)
 SDL_DYNAPI_PROC(void,SDL_ClearQueuedAudio,(SDL_AudioDeviceID a),(a),)
 SDL_DYNAPI_PROC(SDL_Window*,SDL_GetGrabbedWindow,(void),(),return)
+#ifdef __WIN32__
 SDL_DYNAPI_PROC(void,SDL_SetWindowsMessageHook,(SDL_WindowsMessageHook a),(a),)
+#endif