pgsql: Remove spclocation field from pg_tablespace

Remove spclocation field from pg_tablespace

Instead, add a function pg_tablespace_location(oid) used to return
the same information, and do this by reading the symbolic link.

Doing it this way makes it possible to relocate a tablespace when the
database is down by simply changing the symbolic link.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/16d8e594acd96661267cb7897834f9cba51a2ffd

Modified Files
--------------
contrib/pg_upgrade/info.c           |   25 +++++++++++++++-------
contrib/pg_upgrade/tablespace.c     |   18 ++++++++++-----
doc/src/sgml/catalogs.sgml          |    7 ------
doc/src/sgml/func.sgml              |    9 ++++++++
doc/src/sgml/xaggr.sgml             |    4 +-
src/backend/commands/tablespace.c   |    2 -
src/backend/utils/adt/misc.c        |   39 +++++++++++++++++++++++++++++++++++
src/bin/pg_dump/pg_dumpall.c        |   11 +++++++++-
src/bin/psql/describe.c             |   23 ++++++++++++++------
src/include/catalog/catversion.h    |    2 +-
src/include/catalog/pg_proc.h       |    3 ++
src/include/catalog/pg_tablespace.h |   12 ++++------
src/include/utils/builtins.h        |    1 +
13 files changed, 115 insertions(+), 41 deletions(-)