Attached patch updates the route-manager to use FGPositioned to search
for waypoints, instead of a manual airport / fix / navaid search. This
is good because it's now using the 'strictly closest' match, rather
than arbitrarily picking a distant fix over a nearby navaid. In my
case, the TLA VOR is significant to several EGPH procedures, but also
happens to be the ident of a fix a long, long way away.
Also updates the FGPositioned class to stop using Point3D, partly
because it's deprecated and partly because I had misunderstood the
interface and was using it wrong. For now, all FGPositioned distance
checks use SGGeodesy::inverse, which is accurate but inefficient. Once
FGPositioned queries are used for something on a hot path, I'll
probably store the cartesian position as well as the geodetic, to make
these checks fast.
f3b110e565