Bukkit/CraftBukkit — pull request #770 by ScoreUnder (2012-05-13 02:35:39+00:00)
Title: Fix inaccurate head yaw

On long distance teleport (read: one that gets a player into your EntityTracker), if that player is standing still (not rotating their head), their head might appear sideways or even backwards. It will snap back into place when they rotate.
This should fix (work around?) that.

It could be the client's responsibility I suppose, but currently it is not handled that way.