efficiently performing "Dijkstra algorithm".
Durk Talsma: Added the detection of "circular" wait situations in the AI
ground network. A circular wait is a situation where aircraft a waits for
b; b waits for c; and c (in turn) waits for a. The checkCircularWaits
function detects these situations.
The current "solution" to a circular wait is rather crude: Remove the
aircraft from the scene. A proper solution needs a lot more work, however,
and at least this patch stops the AI system from clogging up. in case of a
circular wait.
- Ground network slow-down finally works as expected
(although occasionally causing a traffic jam)
- Hold position instruction now really sets speed to zero, in addition
it actually works now for crossing and two-way traffic
- Attempt to limit execution time of ground network trace algorithm
to make performance acceptable at high-density networks
- Removed remaining terminal messages
- Various minor tweaks and clean-ups
