Zones didn't split when a full window was placed.
Fixed walls not splitting zones.
Added code protecting against obscure merges of invalid zones.
 - Usually happened when welding fuel tanks caused secondary explosions.
Removed a leftover generally-accessible debug verb.
Added Reboot ZAS as a debug verb.
 Replaces the air controller, marks all old zones invalid,
 and adds every turf to the update list. Results are the same as on a
 server start.