Created a global list to track base turfs for explosions/shuttle moves.
Remaps the asteroid to be a moonlet. Tidies up some references to 'asteroid', removes moonbase from the accessible z level list.
New turf proc: assume_gas(). Maps to air.adjust_gas_temp().
Lots of optimizations to processing, fire, lighting, HasEntered() and
more.
Zones now process all fire data and existance in one go, fire objects
only handle spreading.
Most code has been ported straight so some of it mightn't be ideally
structured for the new gas_mixtures.
Signed-off-by: Mloc-Argent <colmohici@gmail.com>
