HDFS-5234 Move RpcFrameDecoder out of the public API. Contributed by Haohui Mai

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1525104 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5231. Fix broken links in the document of HDFS Federation. Contributed by Haohui Mai.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1525133 13f79535-47bb-0310-9956-ffa450edef68