pgsql: Get rid of pg_class.reltoastidxid.

Get rid of pg_class.reltoastidxid.

Treat TOAST index just the same as normal one and get the OID
of TOAST index from pg_index but not pg_class.reltoastidxid.
This change allows us to handle multiple TOAST indexes, and
which is required infrastructure for upcoming
REINDEX CONCURRENTLY feature.

Patch by Michael Paquier, reviewed by Andres Freund and me.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/2ef085d0e6960f5087c97266a7211d37ddaa9f68

Modified Files
--------------
contrib/pg_upgrade/info.c              |   15 ++-
doc/src/sgml/catalogs.sgml             |    9 --
doc/src/sgml/diskusage.sgml            |   26 ++--
doc/src/sgml/monitoring.sgml           |    4 +-
src/backend/access/heap/tuptoaster.c   |  225 +++++++++++++++++++++++++++-----
src/backend/catalog/heap.c             |    1 -
src/backend/catalog/index.c            |   23 +---
src/backend/catalog/system_views.sql   |   10 +-
src/backend/commands/cluster.c         |   34 +++--
src/backend/commands/tablecmds.c       |   20 ++-
src/backend/rewrite/rewriteDefine.c    |    5 +-
src/backend/utils/adt/dbsize.c         |   24 +++-
src/bin/pg_dump/pg_dump.c              |   14 +-
src/include/access/tuptoaster.h        |    9 ++
src/include/catalog/catversion.h       |    2 +-
src/include/catalog/pg_class.h         |   44 +++----
src/test/regress/expected/oidjoins.out |    8 --
src/test/regress/expected/rules.out    |   16 +--
src/test/regress/sql/oidjoins.sql      |    4 -
src/test/regress/sql/rules.sql         |    2 +-
src/tools/findoidjoins/README          |    1 -
21 files changed, 333 insertions(+), 163 deletions(-)