Partitioned hash join.

This is the first patch for partition hash join with spilling. End to end
inner join should be working but this new join operator is disabled by default.

Change-Id: I802117b13258b2bfdef49706e48572f5d395bb72
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3435
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins