Level-builder was treating secret doors as walls when considering isolated regions, fixed.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@4174 c06c8d41-db1a-0410-9941-cceddc491573

Created by  dshaligram  on April 10, 2008
WINPLTSMGJYDSOAB2JRLTNEGMX6AZSZEYXSNMILWKCYVP3JP3LFQC
Change contents