Fix NPCs not giving you the things they said they were giving you.
Prevent warning when entering smoke with proper mouth protection
Prevent some warnings for gas, fixes #259
Smoke field walk-in effect reformat
Less copypasta in mapgen::rotate, and fix vehicle rotation being very wrong on horizontals.

I actually got that set-of-vehicle-pointers-iterator right on the first try? I'm shocked it compiled, let alone worked.
Spread vehicles along the whole width of the road. More collision-looking wrecks, less "that motorcycle teleported into a car" wrecks.
Merge NPC gifting fix, Smoke field warning supression, and vehicle placement fix.

Conflicts:
	field.cpp