Revert idea of zer-padding padding session id in log_line_prefix

Removal of doc adjustment and release note mention as well.
Execute SET TRANSACTION SNAPSHOT during pg_dump
Previous coding set the SQL buffer but never executed

Bug noted by me during beta testing
9.3 release notes:  update from Amit Kapila

No need to mention wal_receiver_status_interval.
9.3 release notes: Add cache of local locks

Mention this also helps in the restoring of pg_dumps.

Jeff Janes
9.3 release notes:  use "restoration"

Andrew Dunstan
Disallow unlogged materialized views.

The initial implementation of this feature was really unsupportable,
because it's relying on the physical size of an on-disk file to carry the
relation's populated/unpopulated state, which is at least a modularity
violation and could have serious long-term consequences.  We could say that
an unlogged matview goes to empty on crash, but not everybody likes that
definition, so let's just remove the feature for 9.3.  We can add it back
when we have a less klugy implementation.

I left the grammar and tab-completion support for CREATE UNLOGGED
MATERIALIZED VIEW in place, since it's harmless and allows delivering a
more specific error message about the unsupported feature.

I'm committing this separately to ease identification of what should be
reverted when/if we are able to re-enable the feature.
Back out some recent translation updates.

Very old versions of msgfmt choke on these specific messages, for reasons
that are unclear at the moment.  Remove them so that we can ship a beta
release and not get complaints from testers (these messages will just go
untranslated, instead, and we're hardly at 100% coverage anyway).
Peter Eisentraut will look for a better fix later.
Move materialized views' is-populated status into their pg_class entries.

Previously this state was represented by whether the view's disk file had
zero or nonzero size, which is problematic for numerous reasons, since it's
breaking a fundamental assumption about heap storage.  This was done to
allow unlogged matviews to revert to unpopulated status after a crash
despite our lack of any ability to update catalog entries post-crash.
However, this poses enough risk of future problems that it seems better to
not support unlogged matviews until we can find another way.  Accordingly,
revert that choice as well as a number of existing kluges forced by it
in favor of creating a pg_class.relispopulated flag column.
Desultory copy-editing of the 9.3 release notes.

I had time for a quick review of the notes, so here are some fixes.
Stamp 9.3beta1.