These methods were removed by mistake in commit 0dbb0dff9, which broke
code that relies on them (e.g., FMSDelegate.currentWaypointChanged() in
$FG_ROOT/Nasal/route_manager.nas).
Also remove 'waypointPrototype' from NasalPositioned.cxx, since it is
not used anymore.
Note: the methods can't be easily re-enabled by means of
'waypointPrototype', because for FPLeg ghosts, 'waypointPrototype'
was emulated as a parent class before this commit, and thus when
querying an FPLeg ghost for its 'airport', 'runway' or 'navaid'
member, the corresponding data member returned by
waypointCommonGetMember() would be found by legGhostGetMember()
*before* parent classes are searched. This commit prevents this
from happening by returning 'airport', 'runway' and 'navaid' as
member functions *directly* in legGhostGetMember(), before
waypointCommonGetMember() is queried as a fallback.
Thanks to Eric van den Berg for the bug report.
c28f63132f