HIVE-6182: LDAP Authentication errors need to be more informative (Szehon via Xuefu)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1558613 13f79535-47bb-0310-9956-ffa450edef68
HIVE-6184 : Bug in SessionManager.stop() in HiveServer2 (Navis via Thejas Nair)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1558614 13f79535-47bb-0310-9956-ffa450edef68
HIVE-6189: Support top level union all statements (patch by Gunther Hagleitner, reviewed by Navis and Harish Butani)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1558615 13f79535-47bb-0310-9956-ffa450edef68