Greenplum patch for estimated rowcounts being wrong.

Greenplum stores the number of rows per segmentDatabase (actually the max of any of the segDBs) in pg_class.reltuples,
notthe total number of tuples. 

This causes the stats to display wrong values, and causes pgAdmin to warn that Analyze is needed when it is not.

This simple patch multiplies the reltuples x gp_segments, so that we get a better value.

Of course, it only does this for Greenplum connections.