Replace insertion sort in contrib/intarray with qsort().
Replace insertion sort in contrib/intarray with qsort().

It's all very well to claim that a simplistic sort is fast in easy
cases, but O(N^2) in the worst case is not good ... especially if the
worst case is as easy to hit as "descending order input".  Replace that
bit with our standard qsort.

Per bug #12866 from Maksym Boguk.  Back-patch to all active branches.

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