Fix incorrect animations when spawning as a transformed creature

Closes #1310

In addition, untransforming on an invalid tile (possible with the Bat in
Polymorphable) will warp the player back to where they initially
transformed. If the transformed on a different map, they'll be
teleported to the spawn position on that map.
Merge pull request #1311 from dorkster/fixes

Fix incorrect animations when spawning as a transformed creature