magicbane groundwork

magicbane groundwork

     To fix Magicbane's message sequencing, its code needs to be redone
substantially.  These changes make that easier.

cancel_monst()  let caller know whether cancellation succeeds
resist()  give artifact weapons a resistance attack rating
vtense()  handle monster names and "you" as subjects; checking against
          object names and descriptions pointed out a couple of other
          words that would have ended up being miscategorized.