Removed DISRUPTION brand and added DRAGON_SLAYING.

The old disruption code should probably be moved over to holy wrath but I'm unsure whether I should replace the current one. I'm talking about the "You are blasted by holy energy!" bit in the commit below. For now, I've simply removed it.

All dragon slaying currently does is what orc slaying does, only against dragons. So no additional effects, resistances or otherwise. Both slaying brands are still randomly created (though dragon only for polearms), I haven't changed anything about that.

Also removed DISTORTION effect upon wielding such a weapon. Xom is still pleased about seeing you in this conundrum, but not as much as when you were blasted right away. Changed distortion description to explicitly mentioning its effects.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@3219 c06c8d41-db1a-0410-9941-cceddc491573

Created by  j-p-e-g  on January 7, 2008
V53DXVC5T3N6J47H2CNG4MMPRR4PHW4AIS66QNVTKJNNYTTTQL4AC
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