Bukkit/CraftBukkit — pull request #510 by amaranth (2011-10-13 23:51:30+00:00)
Title: implementation of Entity.isInvisible and Entity.setInvisible

When an entity is marked as invisible a plugin can control who is able to see
it via EntityTrackEvent. If no plugin handles this event we fallback to letting
op'ed players see invisible entities.

This is the CraftBukkit side of https://github.com/Bukkit/Bukkit/pull/381