Add arena_force_ai option (also settable as "force_ai" or "no_force_ai" in the arena spec) that when unset, uses the real game's monster AI, and when set, forces monsters to attack.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@8160 c06c8d41-db1a-0410-9941-cceddc491573

Created by  dshaligram  on January 3, 2009
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