Allow player to cancel stepping into a dangerous place when it's done

by swapping places with a monster. Fixes [2535944].

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@8748 c06c8d41-db1a-0410-9941-cceddc491573

Created by  haranp  on January 25, 2009
6OA2KACW3DOO2YJB4F7ROHCEY44F2XDFWLGJBF4VOVHTG4VLHJAAC
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