sound.c: Work around desynchronisation between Direct Sound channels and PSG channels while keeping the saved state version at 1.0f. Loading a saved state made while the desynchronisation was less than 186 milliseconds will also fix it. If the desynchronisation was already longer than that, then it may fix itself within an hour of play.
GCW Zero: Dampen sound while fast-forwarding to avoid loud pops.
GCW Zero: Optimise the case where no scaling occurs.

Formerly, it would take 7-9% more CPU time than using pcercuei's scaler. Now it takes 1-3% less CPU time than with the scaler.