create index updates nrows statistics

a create index updates the statistics in pg_class,
this leads to substantial performance degradation compared to
6.4.2.

If you want to see what I mean simply run the performance test in
our test subdirectory.

I think the create index statement should not update this statistic.
(at least not in the newly created empty table case)
This behavior would then be in sync with the create table behavior.

Andreas