Add gen_random_uuid() to contrib/pgcrypto.

This function provides a way of generating version 4 (pseudorandom) UUIDs
based on pgcrypto's PRNG.  The main reason for doing this is that the
OSSP UUID library depended on by contrib/uuid-ossp is becoming more and
more of a porting headache, so we need an alternative for people who can't
install that.  A nice side benefit though is that this implementation is
noticeably faster than uuid-ossp's uuid_generate_v4() function.

Oskari Saarenmaa, reviewed by Emre Hasegeli
Minor code beautification in contrib/sslinfo.

Static-ify some functions that didn't need to be exported, and improve
a couple of comments.

Gurjeet Singh
Fix client-only installation

The psql Makefile was not creating $(datadir) before installing
psqlrc.sample there.

In most cases, the directory would be created in some other way, but for
the documented from-source client-only installation procedure, it could
fail.

Reported-by: Mike Blackwell <mike.blackwell@rrd.com>
Export a few more symbols required for test_shm_mq module.

Patch from Amit Kapila.
Make various variables const (read-only).

These changes should generally improve correctness/maintainability.
A nice side benefit is that several kilobytes move from initialized
data to text segment, allowing them to be shared across processes and
probably reducing copy-on-write overhead while forking a new backend.
Unfortunately this doesn't seem to help libpq in the same way (at least
not when it's compiled with -fpic on x86_64), but we can hope the linker
at least collects all nominally-const data together even if it's not
actually part of the text segment.

Also, make pg_encname_tbl[] static in encnames.c, since there seems
no very good reason for any other code to use it; per a suggestion
from Wim Lewis, who independently submitted a patch that was mostly
a subset of this one.

Oskari Saarenmaa, with some editorialization by me
Allow SET TABLESPACE to database default

We've always allowed CREATE TABLE to create tables in the database's default
tablespace without checking for CREATE permissions on that tablespace.
Unfortunately, the original implementation of ALTER TABLE ... SET TABLESPACE
didn't pick up on that exception.

This changes ALTER TABLE ... SET TABLESPACE to allow the database's default
tablespace without checking for CREATE rights on that tablespace, just as
CREATE TABLE works today.  Users could always do this through a series of
commands (CREATE TABLE ... AS SELECT * FROM ...; DROP TABLE ...; etc), so
let's fix the oversight in SET TABLESPACE's original implementation.
Add ALTER TABLESPACE ... MOVE command

This adds a 'MOVE' sub-command to ALTER TABLESPACE which allows moving sets of
objects from one tablespace to another.  This can be extremely handy and avoids
a lot of error-prone scripting.  ALTER TABLESPACE ... MOVE will only move
objects the user owns, will notify the user if no objects were found, and can
be used to move ALL objects or specific types of objects (TABLES, INDEXES, or
MATERIALIZED VIEWS).
Fix VACUUM's reporting of dead-tuple counts to the stats collector.

Historically, VACUUM has just reported its new_rel_tuples estimate
(the same thing it puts into pg_class.reltuples) to the stats collector.
That number counts both live and dead-but-not-yet-reclaimable tuples.
This behavior may once have been right, but modern versions of the
pgstats code track live and dead tuple counts separately, so putting
the total into n_live_tuples and zero into n_dead_tuples is surely
pretty bogus.  Fix it to report live and dead tuple counts separately.

This doesn't really do much for situations where updating transactions
commit concurrently with a VACUUM scan (possibly causing double-counting or
omission of the tuples they add or delete); but it's clearly an improvement
over what we were doing before.

Hari Babu, reviewed by Amit Kapila
Add CREATE TABLESPACE ... WITH ... Options

Tablespaces have a few options which can be set on them to give PG hints
as to how the tablespace behaves (perhaps it's faster for sequential
scans, or better able to handle random access, etc).  These options were
only available through the ALTER TABLESPACE command.

This adds the ability to set these options at CREATE TABLESPACE time,
removing the need to do both a CREATE TABLESPACE and ALTER TABLESPACE to
get the correct options set on the tablespace.

Vik Fearing, reviewed by Michael Paquier.
Merge branch 'master' of git://git.postgresql.org/git/postgresql