Extensions, patch v17

Hi,

Here's the latest extension's patch.

The only item with still some work to be done on it is the regression
tests support: we're not aiming to full coverage is my understanding,
and installing contribs goes a long way towards testing extensions. Do
we want more? If so, please detail what exactly.

What's in v17:

 - 9700 lines of context diff

   226 files changed, 4919 insertions(+), 326 deletions(-)

 - extension.control.in cleanup

   This file is no longer supported nor mentioned in the docs. The
   version property of the extension.control file has to be managed
   there directly, we no longer offer any support for using any existing
   way to obtain it from the extension's Makefile.

 - psql integration rework

  \dx                    list installed extensions
  \dx[+]  [PATTERN]      list extension's objects
  \dX     [PATTERN]      list installed and available extensions

dim=# \dx
                                         List of extensions
 Schema |     Name      | Version  |                          Description
--------+---------------+----------+----------------------------------------------------------------
 utils  | adminpack     | 9.1devel | Administrative functions for PostgreSQL
 utils  | cube          | 9.1devel | data type for representing multidimensional cubes
 utils  | earthdistance | 9.1devel | calculating great circle distances on the surface of the Earth
 utils  | hstore        | 9.1devel | storing sets of key/value pairs
 utils  | isn           | 9.1devel | data types for the international product numbering standards
 utils  | lo            | 9.1devel | managing Large Objects
(6 rows)

dim=# \dx lo
           Objects in extension "lo"
 Object Class |       Object Description
--------------+---------------------------------
 pg_extension | extension lo
 pg_type      | type utils.lo
 pg_proc      | function utils.lo_oid(utils.lo)
 pg_proc      | function utils.lo_manage()
(4 rows)

dim=# \dx+ lo
                           Objects in extension "lo"
 Object OID | Object ClassOID | Object Class |       Object Description
------------+-----------------+--------------+---------------------------------
      16388 |            3996 | pg_extension | extension lo
      16389 |            1247 | pg_type      | type utils.lo
      16390 |            1255 | pg_proc      | function utils.lo_oid(utils.lo)
      16391 |            1255 | pg_proc      | function utils.lo_manage()
(4 rows)

Regards,
--
Dimitri Fontaine
http://2ndQuadrant.fr     PostgreSQL : Expertise, Formation et Support