Allow interrupting auto-move

[Bumber64]

When auto-moving towards a location while controlling a unit, via clicking on a tile with the mouse or by using the keyboard to auto-move to stairs, the only way to interrupt the process seems to be to exit unit control mode. This should probably be interruptible by just using one of the movement keys.

If the unit's path to the destination is blocked (e.g., by a unit unwilling to move,) auto-move should also automatically be cancelled instead of the unit attempting to wait in place forever.

[miki151]

I think auto-moving does cancel if you click anywhere or press a key, I'll take a look to see if maybe something is broken here.