Fixed bug 3745 - specify SDLCALL as the calling convention for API callbacks

Patches contributed by Ozkan Sezer

include/SDL_hints.h

@@ -903,7 +903,7 @@ extern DECLSPEC SDL_bool SDLCALL SDL_GetHintBoolean(const char *name, SDL_bool d
 /**
  * \brief type definition of the hint callback function.
  */
-typedef void (*SDL_HintCallback)(void *userdata, const char *name, const char *oldValue, const char *newValue);
+typedef void (SDLCALL *SDL_HintCallback)(void *userdata, const char *name, const char *oldValue, const char *newValue);
 
 /**
  *  \brief Add a function to watch a particular hint