pgsql: Allow the pgstat views to show toast tables as well as regular

Log Message:
-----------
Allow the pgstat views to show toast tables as well as regular tables
(the stats system has always collected this info, but the views were
filtering it out).  Modify autovacuum so that over-threshold activity
in a toast table can trigger a VACUUM of the parent table, even if the
parent didn't appear to need vacuuming itself.  Per discussion a month
or so back about "short, wide tables".

Modified Files:
--------------
    pgsql/src/backend/catalog:
        system_views.sql (r1.19 -> r1.20)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/system_views.sql.diff?r1=1.19&r2=1.20)
    pgsql/src/backend/postmaster:
        autovacuum.c (r1.3 -> r1.4)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/autovacuum.c.diff?r1=1.3&r2=1.4)
        pgstat.c (r1.105 -> r1.106)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/pgstat.c.diff?r1=1.105&r2=1.106)
    pgsql/src/include/catalog:
        catversion.h (r1.298 -> r1.299)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.298&r2=1.299)
    pgsql/src/include:
        pgstat.h (r1.35 -> r1.36)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/pgstat.h.diff?r1=1.35&r2=1.36)
    pgsql/src/test/regress/expected:
        rules.out (r1.106 -> r1.107)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/rules.out.diff?r1=1.106&r2=1.107)