In preparation for caching the groundnet in the NavCache, make taxi-nodes and parkings inherit from FGPositioned. As part of this, make them heap (as opposed to value) classes, disable their copy-constructors, remove many mutating operations, and give them real constructors.
Various other patches that have been lingering around for a while:
* Moved trafficcontrol.[ch]xx from the Airports directory to ATC, where
it really belongs.
* AI aircraft will request startup clearance, and ground control will
approve.
* Starting AI Aircraft will be pushed back to a predefined holding point
on the ground network, and wait a while before taxiing out to the runway
Fixed bug due to longstanding inconsistency in FGAirport
getter functions return types.
Durk Talsma: Fixed traffic record initialization bug that occured
when taxiing traffic was waiting for traffic on runway
I refactored the XML loading code out of FGAirportDynamics and
FGRunwayPreference. I also added a new class XMLLoader, which serves as a
facade to the loader functions. Further I changed FGRunwayPreference to just
keep a FGAirport ref, which is more concise and closer to the right(tm)
solution than storing the airport data a second time ;-)
