restoreInitialState methods to FGGlobals, as well as the two-stage
commit described above for loading saved files. fgInit now takes a
snapshot of the initial state before handing off to the main loop, and
the GUI reInit function restores that state explicitly before calling
fgReInit.
The FlightGear patches also modify fg_props.hxx to add optional
useDefault arguments to all of the fgTie functions -- that lets you
choose whether you want to pick up any default value in the property
tree when you tie the property (the default is true).
FGOptions is history, and the modules are (starting) to use the property
manager directly. Let me know if I left any files out.
Inevitably, there will be some problems with broken options, etc.,
that I haven't found in my tests, but I'll try to fix them quickly.
We also need to stress that the property names currently in use are
not stable -- we need to reorganize them a bit for clarity.
