Disallow permanent abominations created via Twisted Resurrection from

taking stairs, and consolidate the logic for this and other stair-ignoring undead in a monsters::can_use_stairs() function.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@7323 c06c8d41-db1a-0410-9941-cceddc491573

Created by  dolorous  on November 1, 2008
6EZYOF7W56XYRLZ7JSIX3DLQS7BOYVQP7TSSCNU7WIJT4FPZIM6QC
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