HIVE-4324 : ORC Turn off dictionary encoding when number of distinct keys is greater than threshold (Kevin Wilfong & Owen Omalley via Ashutosh Chauhan)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1512893 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-HIVE-4779-trunk-gd