HADOOP-9845. Update protobuf to 2.5 from 2.4.x. (tucu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1513281 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-9848. Create a MiniKDC for use with security testing. (ywskycn via tucu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1513308 13f79535-47bb-0310-9956-ffa450edef68