Minor GIN code refactoring.

It makes for cleaner code to have separate Get/Add functions for PostingItems
and ItemPointers.  A few callsites that have to deal with both types need to
be duplicated because of this, but all the callers have to know which one
they're dealing with anyway. Overall, this reduces the amount of casting
required.

Extracted from Alexander Korotkov's larger patch to change the data page
format.
psql: Make \pset without arguments show all settings.

Gilles Darold, reviewed by Pavel Stehule
Add DISCARD SEQUENCES command.

DISCARD ALL will now discard cached sequence information, as well.

Fabrízio de Royes Mello, reviewed by Zoltán Böszörményi, with some
further tweaks by me.
Fix silly thinko in ResetSequenceCaches.

Report from Kevin Hale Boyes.
doc: Add missing words to bgworker docs.

Maciek Sakrejda
Issue error on SET outside transaction block in some cases

Issue error for SET LOCAL/CONSTRAINTS/TRANSACTION outside a transaction
block, as they have no effect.

Per suggestion from Morten Hustveit
isolationtester: Allow tuples to be returned in more places

Previously, isolationtester would forbid returning tuples in
session-specific teardown (but not global teardown), as well as in
global setup.  Allow these places to return tuples, too.
Make some isolationtester specs more complete

Also, make sure they pass on all transaction isolation levels.
add multixact-no-deadlock to schedule
pg_upgrade doc: link mode additions

Mention that link mode uses less disk space, and uses junction points on
Windows.

Backpatch to 9.3.
pgbench: Remove stray use of "float" math.

Oversight in commit 4a87f308b33457670f9ab4bc622678e5d285b9c2.

Fabien COELHO
pgbench: Elaborate latency reporting.

Isolate transaction latency (elapsed time between submitting first
command and receiving response to last command) from client-side delays
pertaining to the --rate schedule.  Under --rate, report schedule lag as
defined in the documentation.  Report latency standard deviation
whenever we collect the measurements to do so.  All of these changes
affect --progress messages and the final report.

Fabien COELHO, reviewed by Pavel Stehule.
Fix various bugs in postmaster SIGKILL processing

Clamp the minimum sleep time during immediate shutdown or crash to a
minimum of zero, not a maximum of one second.  The previous code could
result in a negative sleep time, leading to failure in select() calls.

Also, on crash recovery, reset AbortStartTime as soon as SIGKILL is sent
or abort processing has commenced instead of waiting until the startup
process completes.  Reset AbortStartTime as soon as SIGKILL is sent,
too, to avoid doing that repeatedly.

Per trouble report from Jeff Janes on
CAMkU=1xd3=wFqZwwuXPWe4BQs3h1seYo8LV9JtSjW5RodoPxMg@mail.gmail.com

Author: MauMau
pgbench: Comment on thread timing hazards.

Reviewed by Fabien COELHO.
Document support for VPATH builds of extensions.

Cédric Villemain and me.
Eliminate xmin from hash tag for predicate locks on heap tuples.

If a tuple was frozen while its predicate locks mattered,
read-write dependencies could be missed, resulting in failure to
detect conflicts which could lead to anomalies in committed
serializable transactions.

This field was added to the tag when we still thought that it was
necessary to carry locks forward to a new version of an updated
row.  That was later proven to be unnecessary, which allowed
simplification of the code, but elimination of xmin from the tag
was missed at the time.

Per report and analysis by Heikki Linnakangas.
Backpatch to 9.1.
plpgsql: Add new option print_strict_params.

This option provides more detailed error messages when STRICT is used
and the number of rows returned is not one.

Marko Tiikkaja, reviewed by Ian Lawrence Barwick
Make DISCARD SEQUENCES also discard the last used sequence.

Otherwise, we access already-freed memory.  Oops.

Report by Michael Paquier.  Fix by me.
Translation updates
Fix bugs in SSI tuple locking.

1. In heap_hot_search_buffer(), the PredicateLockTuple() call is passed
wrong offset number. heapTuple->t_self is set to the tid of the first
tuple in the chain that's visited, not the one actually being read.

2. CheckForSerializableConflictIn() uses the tuple's t_ctid field
instead of t_self to check for exiting predicate locks on the tuple. If
the tuple was updated, but the updater rolled back, t_ctid points to the
aborted dead tuple.

Reported by Hannu Krosing. Backpatch to 9.1.