Actually pay attention to the affects_nothing member, so that retraced beams

won't affect the beam's source, so that weapons of returning won't damage their thrower upon returning.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@8367 c06c8d41-db1a-0410-9941-cceddc491573

Created by  zelgadis  on January 9, 2009
3XIWOQS6UF3W4P2VX47BIP6X2G3BF7WVZILF74PY3HOTEXIKW6BAC
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