dealing with Zot miscasts and the like, since many actor interfact functions require a valid source on the monster side. This way, for example, divination miscasts will use the monster's own HD when confusing. With kill_category and kill_type set as they are, no one should get improper credit for any kills caused by Zot traps. Also, if the player worships TSO and gets the "poisonous cloud" Zot miscast, any monsters poisoned from it will not trigger the poisoning conduct.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@8567 c06c8d41-db1a-0410-9941-cceddc491573