pgsql: Support having multiple Unix-domain sockets per postmaster.

Support having multiple Unix-domain sockets per postmaster.

Replace unix_socket_directory with unix_socket_directories, which is a list
of socket directories, and adjust postmaster's code to allow zero or more
Unix-domain sockets to be created.

This is mostly a straightforward change, but since the Unix sockets ought
to be created after the TCP/IP sockets for safety reasons (better chance
of detecting a port number conflict), AddToDataDirLockFile needs to be
fixed to support out-of-order updates of data directory lockfile lines.
That's a change that had been foreseen to be necessary someday anyway.

Honza Horak, reviewed and revised by Tom Lane

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/c9b0cbe98bd783e24a8c4d8d8ac472a494b81292

Modified Files
--------------
doc/src/sgml/client-auth.sgml                 |    2 +-
doc/src/sgml/config.sgml                      |   35 +++++---
doc/src/sgml/ref/postgres-ref.sgml            |   10 ++-
doc/src/sgml/runtime.sgml                     |    2 +-
src/backend/libpq/pqcomm.c                    |   92 +++++++++++++-------
src/backend/postmaster/postmaster.c           |   75 ++++++++++++----
src/backend/tcop/postgres.c                   |    2 +-
src/backend/utils/adt/varlena.c               |  110 ++++++++++++++++++++++
src/backend/utils/init/miscinit.c             |  120 +++++++++++++++---------
src/backend/utils/misc/guc.c                  |   12 ++-
src/backend/utils/misc/postgresql.conf.sample |    3 +-
src/bin/initdb/initdb.c                       |   11 ++-
src/bin/pg_ctl/pg_ctl.c                       |    2 +-
src/include/libpq/libpq.h                     |    8 +-
src/include/miscadmin.h                       |    7 +-
src/include/postmaster/postmaster.h           |    2 +-
src/include/utils/builtins.h                  |    2 +
17 files changed, 369 insertions(+), 126 deletions(-)