Music fast forward support

Some game cutscenes may wait until the music ends before continuing or may wait music to get a specific tick before continuing a sequence, this makes fast forward function useless for those games.

Game test: Asterbee (demo), by Slade: download, forum post. Select "no" to not skip the intro, press F and keypad + to skip, then the cutscene will wait until music ends.

An approach to implement this could be by updating the music playback position based on skipped frame count while the fast forward is active, and taking care of properly syncing once the fast forward ends.