Tolerate Octree leaf children which have been moved outside their leaf's BBox. This is necessary since lazy-loading of ILS and threshold files can cause re-locations even during child traversal, where updating the hierarchy is very complex. Instead, simply tolerate this case, and rely on the real position data (which is correct).
Make landings and takeoffs look more correct; tweak climb-out and touchdown phases in particular, so the turn to destination heading occurs earlier on climb out, and touchdown occurs close the GS transmitter / some distance down the runway from the beginning.
Avoid the application becoming unresponsive during nav-cache rebuilds. We still have to wait for the rebuild, but perform it on a helper thread so the main GUI thread stays responsive and hence doesn't trigger a beach-ball / 'not responding' alert. Also ensures there's some feedback (the spinner) during the rebuild operation, so users don't think we've hung.
Cache the parsed navigation and airport data in a binary file to reduce
startup times and memory consumption (since only referenced FGPositioned
elements are held in memory).
Data will be reimported when the mod-time of any input file is changed.
If a global file is changed (nav.dat, awy.dat, apt.dat, etc), the cache
will be completely rebuilt, which takes approximately 30 seconds on
moderate hardware. (Future work may reduce this).
