Mobs can't pickup items

Mobs that previously had the ability to pick up items (zombies, skeletons, zombie pigmen etc.) no longer can.

To reproduce:
1. Fill a hole with a ton of zombies. Tons of them. No, even more than that.
2. Chuck a bunch of your favorite item into the hole.
3. Move far enough away for the mobs to despawn.
4. Return to hole. Ta-da! The mobs are gone, but your items are there, completely untouched!