HIVE-4435 : Column stats: Distinct value estimator should use hash functions that are pairwise independent (Shreepadma Venugopalan via Ashutosh Chauhan)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1490323 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/trunk' into trunk-gd
Merge remote branch 'origin/trunk-gd' into fb-YAHOO-321-trunk-gd