Commuter airport: Small. 5x4. 3 terminals, 2 helipads.
Intercontinental: massive. 9x11. 8 terminals, 2 helipads, 4 runways.
Helidepot: a small heliport with a depot for helis only.
Helistation: a large heliport with 3 helipads and a depot.
- CodeChange: changed the airport gui airport-type checking. Added function GetValidAirports() that returns bitmasked availibility, is also used for checking.
- CodeChange: to check tree-planting, 2 const arrays have been moved to table/tree_land.h (type and count)
- CodeChange: added IsTownIndex() in following of IsStationIndex(), etc.
- Fix (regression): road tunnels did not work anymore, forgot that their type was 0x200 (documented now)