engine to c now compiles with some manual intervention (as of
bug #596)
So. Some themes have objects that seem to be large natural extensions of the landscape. Masks allow maintaining that. Lemme know if it doesn't look good. If it doesn't, can still use for ice/bounce/indestructible. Indestructible bunker object for example.
Fix AI collision detection with crates and overlapping hedgehogs. Remove duplicating code