HIVE-7143 : Add Streaming support in Windowing mode for more UDAFs (min/max, lead/lag, fval/lval) (Harish Butani via Ashutosh Chauhan)

git-svn-id: https://svn.apache.org/repos/asf/hive/trunk@1601146 13f79535-47bb-0310-9956-ffa450edef68