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

Patches contributed by Ozkan Sezer

include/SDL_surface.h

@@ -94,8 +94,8 @@ typedef struct SDL_Surface
 /**
  * \brief The type of function used for surface blitting functions.
  */
-typedef int (*SDL_blit) (struct SDL_Surface * src, SDL_Rect * srcrect,
-                         struct SDL_Surface * dst, SDL_Rect * dstrect);
+typedef int (SDLCALL *SDL_blit) (struct SDL_Surface * src, SDL_Rect * srcrect,
+                                 struct SDL_Surface * dst, SDL_Rect * dstrect);
 
 /**
  *  Allocate and free an RGB surface.