[C] Tracking code for entities to fix ghosting with entities. Fixes BUKKIT-2471

**Issue:**
When calling Entity.teleport(), Minecraft seems to forget to re-track some EntityTypes, which causes them to leave a ghost copy in the original world.
This patch is supposed to fix that by forcing the tracking code onto all teleported entities. This will cause no problems until Mojang adds EntityTypes which are untrackable.

**Explanation:**
+L202: Document what it does.
+L203: Teleport the entity.

**Relevant Tickets:**

* BUKKIT-2471 - https://bukkit.atlassian.net/browse/BUKKIT-2471
* BUKKIT-1496 - https://bukkit.atlassian.net/browse/BUKKIT-1496