Added the xtern annotation for pbzip2.
Added the xtern annotation for pbzip2.

columbia/xtern,hemingcui/xtern_with_paxos,hemingcui/xtern_with_paxos,columbia/xtern,hemingcui/xtern_with_paxos,hemingcui/xtern_with_paxos,columbia/xtern,columbia/xtern,hemingcui/xtern_with_paxos,columbia/xtern,columbia/xtern