YARN-837. Moved yarn.ClusterInfo into MapReduce project as it doesn't belong to YARN. Contributed by Zhijie Shen.
svn merge --ignore-ancestry -c 1493676 ../../trunk/


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1493677 13f79535-47bb-0310-9956-ffa450edef68
Merge -c 1493693 from trunk to branch-2 to fix HADOOP-9517. Documented various aspects of compatibility for Apache Hadoop. Contributed by Karthik Kambatla.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1493694 13f79535-47bb-0310-9956-ffa450edef68