Support xtern 32bits.
Support xtern 32bits.

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