GCW0: Remove config.h and move its contents to burner_sdl.h
GCW0: Add config path to paths.cpp
GCW0: Fix VideoClear() in sdlvideo.cpp
GCW0: Add saving config for remapped keys.
GCW0: Clear screen properly on gui enter/exit; Also hackfix the timer value so the framerate doesn't drop after exit from gui.
GCW0: Move some externs and prototypes to burner_sdl.h