Pluralize words ending in "folk" (e.g. "merfolk") by leaving them alone

instead of adding "s".

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@5481 c06c8d41-db1a-0410-9941-cceddc491573

Created by  dolorous  on June 4, 2008
6MYUQ5XJZGFQI75LDCTQJ34JDENQCAQANQOAKAA67PRZCEFIOFKQC
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