aar.nas disables $FG_ROOT/Nasal/fuel.nas' main loop, as it should be able
to fully replace it. Ideally, there would be no aar.nas at all, and fuel.nas
would do the job for YASim & JSBSim. Unfortunately, there's a problem with
fuel.nas that's not easy to fix ...
far as this supports air refueling at all)
- make listeners keep variables up-to-date (for better performance)
- remove the ugly initialization stuff in the main loop, but wait in
an extra loop for the FDM to come up
This script works now with the a4f, too. The vulcan2 is *supposed* to
work, but there's apparently a bug in it that prevents it.
/systems/refuel/contact is correcly set, and that should be enough for it.
