[WIP] Car roofs

Show car roof when not boarding it.
Added as pool request mostly to get feedback. Requires a little change in z_orders system, because roof mustn't be displayed upon external door tiles.

Also, a little planning mistake arises: all car trunks are treated as outside a vehicle, i.e. when you step into any car's trunk, you see roof instead of car's insides (unlike when standing on car's open door)

UPD: it doesn't look perfect, but I think it is anyways better than the previous state.
UPD2:
 - [x] Vehicle roofs
  - [x] Show roofs
  - [x] Remove roof tiles from vehicle borders
  - [x] Vehicle construction mode
  - [x] Interior lighting fix
 - [ ] Vehicle fixes
  - [ ] Replace misplaced trunks with cargo carriers (e.g.: flatbed, cube van)
  - [ ] Replace flatbed truck's spawns with pickup trucks
  - [ ] Fix wrong roof tiles on vehicles (e.g. mishappen non-armored tiles in the middle of a humvee roof, IINM)
  - [ ] Fix trunks — must be treated as boardable? so that the game won't draw a roof while you're in the middle of the vehicle