gone. This is good news, since the old query was implemented as a linear
search, sorted by Manhattan distance, and with a warning not to use the logic
at runtime. Various systems (such as the Mk-VIII) do query such data often,
eg every second.
Also gets Point3D out of Airports/simple.hxx, as a precursor to removing it
completely.
- this exposed a bizarre issue on Mac where dragging in <AGL/agl.h> in
extensions.hxx was pulling in all of Carbon to the global namespace
- very scary. As a result, I now need to explicitly include CoreFoundation
in fg_init.cxx.
- change SG_USING_STD(x) to using std::x