fix #H4179 - death reason for rotted globs

fix #H4179 - death reason for rotted globs

'Poisoned by a rotted gray ooze corpse' should have been
'Poisoned by a rotted glob of gray ooze'.

eatcorpse() is called for non-corpse globs and then corpse_xname()
is called for them too to set up death reason for make_sick(), but
it didn't know anything about globs.  Now it does.  Blob size is
ignored since it's not relevant for cause of death.