Spotted when fixing the Rogue level digging/phasing bug: pet movement
was setting up the wrong flag for pets who happened to be carrying a key.
This wasn't particularly noticeable because they tended to drop keys right
after picking them up. And apparently the checks elsewhere in movement
prevented that wrong flag from having any effect; once I changed it so that
pets would hang on to keys, I never saw them break a door down with one.
Now they'll keep keys, similar to unicorn horns and pick-axes, and use them
properly. The door unlocking message needed a tweak because it assumed
that the opener was on the far side trying to reach you and looked quite
odd when you could see the action taking place.
I've put this into the fixes file as a new feature rather than a fix.
c1393e508f