This was inconsistent and had no particular benefits. The only minor
benefit I can see is that it prevents smaller enemies from hiding
inside bigger enemies, and in my test run through Spirit, this only
happened once. Not at all significant compared to how incredibly
awkward the aliens look when they're acting as if they can't move
through other ships.
This commit also includes more function name changes and other minor
style fixes.
In most cases, this has also resulted in limits being lifted. (The
only place I haven't done this is for planets in intermission.cpp,
but I think I'll take away that 10-planet limit as well.)