HIVE-6447 : Bucket map joins in hive-tez (Vikram Dixit, reviewed by Harish Butani, Gunther Hagleitner)

git-svn-id: https://svn.apache.org/repos/asf/hive/branches/branch-0.13@1582613 13f79535-47bb-0310-9956-ffa450edef68