HDFS-4518. Add missing CHANGES.txt description

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1453052 13f79535-47bb-0310-9956-ffa450edef68
HDFS-4519. Support overriding jsvc binary and log file locations when launching secure datanode. Contributed by Chris Nauroth.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1453053 13f79535-47bb-0310-9956-ffa450edef68
MAPREDUCE-5028. Maps fail when io.sort.mb is set to high value. (kkambatl via tucu)

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1453107 13f79535-47bb-0310-9956-ffa450edef68