Add "forget level" command to manual, and change wording of

the deformed body mutation for Centaurs and Nagas (FR 1814790).

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@2538 c06c8d41-db1a-0410-9941-cceddc491573

Created by  j-p-e-g  on October 24, 2007
WF3F2I73VYD5BGLTUC3YWXZQ3CN2H2ZPBH2R7WJ5WQLHJSUYGU5QC
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