melee attacks, disallow giant eyeballs from being zombified, but go on allowing butterflies and brain worms to be zombified.

Rationale: Nothing else in the giant eyeball category can be zombified.
However, everything else in the "batty monster" and worm categories can be zombified. (Besides, regarding the former, summoning butterflies is more about putting barriers between you and monsters, so creating butterfly zombies should do the same.)

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@9138 c06c8d41-db1a-0410-9941-cceddc491573