Fix bomb not to wipe out plane updates while asking for targets

Fix bomb not to wipe out plane updates while asking for targets

The commands to fly planes read the planes into a plane list, and
write them back when they land.  If a plane changes in the file while
it is in that plane list, the changes get wiped out when the plane
lands, triggering a seqno oops.

This is not an issue as long as the complete sortie runs
uninterrupted, because that code takes care to update flying planes
only through the appropriate plane list.

However, the bomb command suspends the planes on a pinpoint bombing
run mid-air over the target sector to let the player choose targets.
This lets code run that *can* update flying planes, for instance the
edit command.

Fix by aborting changed planes, taking care not to clobber the
changes.