Digestion attack can grant hero intrinsics

Digestion attack can grant hero intrinsics

Monster purple worms can now gain intrinsics from swallowing foes whole,
so maybe the hero should be able to do so too.  Intrinsics aren't
granted immediately upon swallowing (that would probably have been
easier), but only once a corpse is created and then entirely digested.

I'm not sure if this is too powerful and was being avoided deliberately
for that reason, since it includes potential level gain from wraith
corpses in addition to other intrinsics.  That's consistent with monster
purple worms but may be a bit too much in the hands of the hero, though
it is limited by needing the corpse creation roll to succeed.