feedback for failed movement attempts

feedback for failed movement attempts

When underwater and an attempt to move onto adjacent land fails
because the destination is a wall or solid rock or closed door,
report that there's an obstacle instead of just silently failing
to make the move.

If the user has 'mention_walls' option set, give feedback for
failing to move diagonally into or out of a doorway instead of
just silently not moving.

Having 'mention_walls' set could yield "you cannot pass through
the bars" when travel was testing (not moving) for a path past
iron bars, and when it happened it tended to be delivered a whole
bunch of times.