pgsql: Add DROP INDEX CONCURRENTLY [IF EXISTS], uses ShareUpdateExclusi

Add DROP INDEX CONCURRENTLY [IF EXISTS], uses ShareUpdateExclusiveLock

Branch
------
master

Details
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http://git.postgresql.org/pg/commitdiff/8cb53654dbdb4c386369eb988062d0bbb6de725e

Modified Files
--------------
doc/src/sgml/ref/drop_index.sgml           |   25 +++++-
src/backend/catalog/dependency.c           |   45 +++++++---
src/backend/catalog/index.c                |  139 ++++++++++++++++++++++++++-
src/backend/commands/tablecmds.c           |   41 ++++++++-
src/backend/nodes/copyfuncs.c              |    1 +
src/backend/nodes/equalfuncs.c             |    1 +
src/backend/parser/gram.y                  |   45 +++++++++
src/backend/tcop/utility.c                 |    7 +-
src/backend/utils/cache/relcache.c         |    6 +
src/include/catalog/dependency.h           |    1 +
src/include/catalog/index.h                |    2 +-
src/include/nodes/parsenodes.h             |    1 +
src/test/regress/expected/create_index.out |   28 ++++++
src/test/regress/sql/create_index.sql      |   21 ++++
14 files changed, 337 insertions(+), 26 deletions(-)