SCUMM: Maniac V0: Original Walk Code Implementation

The original walk code has been implemented so that actors walk exactly as they did on the C64
This also fixes a couple of issues which were occurring,

1. When the actor moved from 1 walk box to the next it caused the actor to 'step' without changing position (just noticed that this problem is also occurring on V1/V2 MM, but not in the original engines)

2. Rapidly changing destination while walking would cause the actor animation to re-start every click (not progressing position)

3. When an actor began walking, the first position change would occur before the walk animation began (so they appeared to 'jump')

4. When the 'xfrac' variable overflowed, the actor position would slightly change on next position update

All V0 hacks made redundant have been removed from the various V2+ functions