github pull request #113 - shopkeeper placement

github pull request #113 - shopkeeper placement

Fixes #113

Incorporate the contents of pull request #113 to fix shopkeeper setup
for irregularly shaped shop rooms.  Code intending to adjust the Y
coordinate was erroneously incrementing the X one instead.  (I'm not
sure whether we have any irregular shops at all but if so, they don't
have the necessary orientation to trigger this bug.)

And add a couple of formatting tweaks in the vicinity....