Review: Display number of changed rows since last analyze

This is a review of the patch in 5192D7D2.8020605@catalyst.net.nz

The patch applies cleanly (with the exception of catversion.h of course),
compiles without warnings and passes the regression tests.

It contains enough documentation, though I'd prefer
"Estimated number of rows modified since the table was last analyzed"
to
"Estimated number of row changes (inserts + updates + deletes) since the last analyze"

The patch works as it should, and I think that this is a
useful addition.  It only exposes a value that is already
available internally, so there shouldn't be any penalties.

I think that the column name is ok as it is, even if it
is a bit long - I cannot come up with a more succinct
idea.  Perhaps "n_changed_since_analyze" could be shortened
to "n_mod_since_analyze", but that's not much of an improvement.

This is a very simple change, and I'll mark this patch "ready for committer".

Yours,
Laurenz Albe