Get rid of any toast table when converting a table to a view.

Also make sure other fields of the view's pg_class entry are appropriate
for a view; it shouldn't have relfrozenxid set for instance.

This ancient omission isn't believed to have any serious consequences in
versions 8.4-9.2, so no backpatch.  But let's fix it before it does bite
us in some serious way.  It's just luck that the case doesn't cause
problems for autovacuum.  (It did cause problems in 8.3, but that's out
of support.)

Andres Freund
Add a materialized view relations.

A materialized view has a rule just like a view and a heap and
other physical properties like a table.  The rule is only used to
populate the table, references in queries refer to the
materialized data.

This is a minimal implementation, but should still be useful in
many cases.  Currently data is only populated "on demand" by the
CREATE MATERIALIZED VIEW and REFRESH MATERIALIZED VIEW statements.
It is expected that future releases will add incremental updates
with various timings, and that a more refined concept of defining
what is "fresh" data will be developed.  At some point it may even
be possible to have queries use a materialized in place of
references to underlying tables, but that requires the other
above-mentioned features to be working first.

Much of the documentation work by Robert Haas.
Review by Noah Misch, Thom Brown, Robert Haas, Marko Tiikkaja
Security review by KaiGai Kohei, with a decision on how best to
implement sepgsql still pending.
Remove accidentally-committed .orig file.