doc: A few awkward phrasing fixes

Josh Kupershmidt
doc: Small tweak for consistency

submitted by "Lyle"
Fix SQL function execution to be safe with long-lived FmgrInfos.

fmgr_sql had been designed on the assumption that the FmgrInfo it's called
with has only query lifespan.  This is demonstrably unsafe in connection
with range types, as shown in bug #7881 from Andrew Gierth.  Fix things
so that we re-generate the function's cache data if the (sub)transaction
it was made in is no longer active.

Back-patch to 9.2.  This might be needed further back, but it's not clear
whether the case can realistically arise without range types, so for now
I'll desist from back-patching further.
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.
Fix map_sql_value_to_xml_value() to treat domains like their base types.

This was already the case for domains over arrays, but not for domains
over certain built-in types such as boolean.  The special formatting
rules for those types should apply to domains over them as well.
Per discussion.

While this is a bug fix, it's also a behavioral change that seems likely
to trip up some applications.  So no back-patch.

Pavel Stehule