Vaccum and analyze counters in pgstat

Attached is a patch that adds columns to pg_stat_*_tables for number
of [auto]vacuum and [auto]analyze runs on a table, completing the
current one that just had the last time these ran. It's particularly
useful to see how much autovac is doing on the tables, but I included
the counts of regular vacuum and analyze as well for completeness.

Comments?

-- 
 Magnus Hagander
 Me: http://www.hagander.net/
 Work: http://www.redpill-linpro.com/