Pen memory leak at shutdown

[slouken]

I haven't checked the other backends, but the X11 backend leaks pen handles.

SDL_QuitPen() gets called before X11_QuitPen(), so there aren't any pens left to clean up and the X11 handles are leaked.

I'm not sure the best way to handle this. Maybe add a cleanup callback to the AddPen call? Why don't we run into this with other types of devices?

[icculus]

We probably just need to move the SDL_QuitPen() call in SDL_VideoQuit() down below the call to _this->VideoQuit(_this); so the backends get first shot at cleaning up system handles.

[slouken]

Should we do that for all the SDL_Quit*?