A long overdue update.

- Finally added handling for sideview screens
- Improved movement functions a bit (in particular, 4-way walking should work much better now)
- Added GHF_FULL_TILE_MOVEMENT, which makes the enemy consider a combo completely solid if any quadrant of it is
- Various bug fixes


I'm still only so happy with the movement functions. I was thinking about rewriting them completely, but that's proven rather tricky, so it'll have to wait for the next version.
There's no handling yet for the No Ground Enemies combo and flag. I might just have GHF_NO_FALL control that, or maybe it could depend on the enemy type being Other (Floating). Any other ideas?