Turn off sign-comparison checks for now until I can figure out what's going on

with Xcode 3.1 + yacc; we didn't always get sign-comparison errors here, and it's pretty annoying.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@6231 c06c8d41-db1a-0410-9941-cceddc491573

Created by  nlanza  on June 29, 2008
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