Added link in header comment.

include/SDL_video.h

@@ -789,6 +789,7 @@ extern DECLSPEC int SDLCALL SDL_UpdateWindowSurface(SDL_Window * window);
  *  \return 0 on success, or -1 on error.
  *
  *  \sa SDL_GetWindowSurface()
+ *  \sa SDL_UpdateWindowSurface()
  */
 extern DECLSPEC int SDLCALL SDL_UpdateWindowSurfaceRects(SDL_Window * window,
                                                          const SDL_Rect * rects,