Signed/unsigned comparison build fix for gcc pickiness -- ARRAYSIZE wraps

sizeof(), which is unsigned.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@2118 c06c8d41-db1a-0410-9941-cceddc491573

Created by  nlanza  on September 16, 2007
GUU3TNB4MKZDZWA3LL32GK2LQONRRSX3M5B4UBMZWU7GDJT54A3QC
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