Makes sure the given area is updated on the given screen.
The rectangle must be confined within the screen boundaries (no clipping is done).
If 'x', 'y', 'w' and 'h' are all 0, SDL_UpdateRect will update the entire screen.
These functions should not be called while 'screen' is locked.
Binds to C-function call in SDL_video.h:
extern DECLSPEC void SDLCALL SDL_UpdateRect (SDL_Surface *screen, Sint32 x, Sint32 y, Uint32 w, Uint32 h)