Randart reverted to additive MR.

(and by the way, I forgot to note that the previous commit could break saves)

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@1919 c06c8d41-db1a-0410-9941-cceddc491573

Created by  haranp  on July 23, 2007
4HNVBCODEZSNIAVXS2ATJVABR2VGFAW55EOEIUOMYCYFA3TB27OQC
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