[need testing] allow switching places

[igroglaz]

we got plenty of people online and blocking tavern and shops become a big issue as people go afk sometimes...

based at this two old posts:
http://angband.oook.cz/forum/showpost.php?p=135423&postcount=32
http://angband.oook.cz/forum/showpost.php?p=135431&postcount=35

the solution came at last:
make it possible to switch places only if there is no damaging terrain (including water)

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PW: I prefer keeping MAng's current behavior where you still can switch places when you run. Blocking on purpose should just be reported and dealt as innappropriate behavior (just add a rule).

I'm not sure that running helps in all occasions. It depends on character direction... need to test