pgsql: Add new system view, pg_config

Add new system view, pg_config

Move and refactor the underlying code for the pg_config client
application to src/common in support of sharing it with a new
system information SRF called pg_config() which makes the same
information available via SQL. Additionally wrap the SRF with a
new system view, as called pg_config.

Patch by me with extensive input and review by Michael Paquier
and additional review by Alvaro Herrera.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/a5c43b886942e96ec5c745041f2d6a50c3205147

Modified Files
--------------
doc/src/sgml/catalogs.sgml           |  52 +++++
src/backend/catalog/system_views.sql |   6 +
src/backend/utils/misc/Makefile      |   4 +-
src/backend/utils/misc/pg_config.c   | 103 +++++++++
src/bin/pg_config/Makefile           |  14 --
src/bin/pg_config/pg_config.c        | 429 ++++-------------------------------
src/common/Makefile                  |  19 +-
src/common/config_info.c             | 206 +++++++++++++++++
src/include/catalog/catversion.h     |   2 +-
src/include/catalog/pg_proc.h        |   4 +
src/include/common/config_info.h     |  21 ++
src/include/port.h                   |   1 +
src/include/utils/builtins.h         |   3 +
src/port/path.c                      |  30 +++
src/test/regress/expected/rules.out  |   3 +
src/tools/msvc/Mkvcbuild.pm          |   4 +-
16 files changed, 491 insertions(+), 410 deletions(-)