More code cleanups and type safety.

Fixed a semi-bug (undefined behaviour) in undead_cannot_memorise().

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@1302 c06c8d41-db1a-0410-9941-cceddc491573

Created by  haranp  on April 14, 2007
KOSAQXB3KF6VAYTG2TOTHGJBB3F7AL6O32EMCXPVZJ5WHQX6XR5AC
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