floor access

floor access

     A post-3.4.3 change dealing with reaching into pits resulted in "you
sit on the air" if you used the #sit command after escaping a pit trap.
Change can_reach_floor() so that caller explicitly controls whether being
on the brink of a pit is a condition that prevents reaching the floor.
This also splits a fairly common message about not being able to reach the
floor into a separate routine.

     There is still oddness here:  if you're polymorphed into a flyer,
#sit yields "you sit down" followed by "you fly over a pit" (latter occurs
when escaping trap activation).  A ceiling hider behaves similarly, but
the second message is "you escape a pit" and doesn't sound quite as silly.
Perhaps #sit should pass TOOKPLUNGE to dotrap(), or maybe there's some
better way to handle this?