MAPREDUCE-5130. Add missing job config options to mapred-default.xml (Ray Chiang via Sandy Ryza)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1619631 13f79535-47bb-0310-9956-ffa450edef68
HADOOP-8896. Javadoc points to Wrong Reader and Writer classes in SequenceFile (Ray Chiang via aw)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-2@1619633 13f79535-47bb-0310-9956-ffa450edef68