alternate bear trap fix

alternate bear trap fix

Fix the situation of Flying hero failing to untrap a bear trap that
was resulting in the trap becoming hidden.  Previous fix prevented
hero from moving onto the trap's location so that the reason for
hiding it didn't occur.  This moves the hero and forces the trap,
so it will become unhidden again before there's any chance to notice
that it had been hidden.

Status 'Flying' conflicts with being trapped at floor level, but that
is a separate, known issue.  I'll have to resurrect my unfinished fix
for that sooner rather than later.