SDL_thread.h: use SDL_ThreadFunction for SDL_CreateThreadWithStackSize

include/SDL_thread.h

@@ -129,7 +129,7 @@ SDL_CreateThread(SDL_ThreadFunction fn, const char *name, void *data,
                  pfnSDL_CurrentEndThread pfnEndThread);
 
 extern DECLSPEC SDL_Thread *SDLCALL
-SDL_CreateThreadWithStackSize(int (SDLCALL * fn) (void *),
+SDL_CreateThreadWithStackSize(SDL_ThreadFunction fn,
                  const char *name, const size_t stacksize, void *data,
                  pfnSDL_CurrentBeginThread pfnBeginThread,
                  pfnSDL_CurrentEndThread pfnEndThread);