Replace int with uint64 in grow_unsorted_array
Replace int with uint64 in grow_unsorted_array

In situations in which our available memory is much larger than the
memory in our sortcontext, it was previously possible to overflow the
maxNumEntries variable.

Signed-off-by: Haisheng Yuan <d24d5fc9e8498fe12c79f514db1a69a6d06b8a3c@pivotal.io>

lisakowen/gpdb,lisakowen/gpdb,yuanzhao/gpdb,lisakowen/gpdb,ashwinstar/gpdb,50wu/gpdb,jmcatamney/gpdb,edespino/gpdb,edespino/gpdb,xinzweb/gpdb,ashwinstar/gpdb,lisakowen/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,edespino/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,xinzweb/gpdb,jmcatamney/gpdb,Chibin/gpdb,yuanzhao/gpdb,Chibin/gpdb,edespino/gpdb,adam8157/gpdb,edespino/gpdb,adam8157/gpdb,50wu/gpdb,ashwinstar/gpdb,yuanzhao/gpdb,adam8157/gpdb,greenplum-db/gpdb,adam8157/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,lisakowen/gpdb,Chibin/gpdb,50wu/gpdb,edespino/gpdb,lisakowen/gpdb,ashwinstar/gpdb,Chibin/gpdb,greenplum-db/gpdb,Chibin/gpdb,Chibin/gpdb,yuanzhao/gpdb,ashwinstar/gpdb,xinzweb/gpdb,ashwinstar/gpdb,50wu/gpdb,50wu/gpdb,jmcatamney/gpdb,Chibin/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,lisakowen/gpdb,xinzweb/gpdb,Chibin/gpdb,greenplum-db/gpdb,yuanzhao/gpdb,adam8157/gpdb,lisakowen/gpdb,xinzweb/gpdb,Chibin/gpdb,adam8157/gpdb,jmcatamney/gpdb,xinzweb/gpdb,50wu/gpdb,Chibin/gpdb,edespino/gpdb,jmcatamney/gpdb,yuanzhao/gpdb,edespino/gpdb,xinzweb/gpdb,yuanzhao/gpdb,edespino/gpdb,jmcatamney/gpdb,50wu/gpdb,edespino/gpdb,adam8157/gpdb,adam8157/gpdb,ashwinstar/gpdb,yuanzhao/gpdb,yuanzhao/gpdb,xinzweb/gpdb,jmcatamney/gpdb,50wu/gpdb