HDFS-5265. Namenode fails to start when dfs.https.port is unspecified. Contributed by Haohui Mai.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1527093 13f79535-47bb-0310-9956-ffa450edef68
HDFS-5260. Merge zero-copy memory-mapped HDFS client reads to trunk and branch-2. Contributed by Chris Nauroth.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1527113 13f79535-47bb-0310-9956-ffa450edef68