HIVE-7677 - Implement native HiveReduceFunction (Chengxiang Li via Brock) [Spark Branch]

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1618094 13f79535-47bb-0310-9956-ffa450edef68
HIVE-7659 - Unnecessary sort in query plan (Rui Li via Brock) [Spark Branch]

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/spark@1618095 13f79535-47bb-0310-9956-ffa450edef68
Merge remote-tracking branch 'upstream/spark' into spark