Figure out what to do with ceilings

[jahu00]

Its' not a high priority, but some footholds appear to be ceilings (like in map 100000001).

[jahu00]

Ceilings might have their X1 and X2 flipped. Normally X1 is < X2 but for ceiling reverse appears to be true.

[jahu00]

This is probably something to resolve later when player avatar gets drawn, as collision would be based on bounding box rather than position alone (the way the rest of physics is handled right now).