pgsql: Rethink behavior of CREATE OR REPLACE during CREATE EXTENSION.

Rethink behavior of CREATE OR REPLACE during CREATE EXTENSION.

The original implementation simply did nothing when replacing an existing
object during CREATE EXTENSION.  The folly of this was exposed by a report
from Marc Munro: if the existing object belongs to another extension, we
are left in an inconsistent state.  We should insist that the object does
not belong to another extension, and then add it to the current extension
if not already a member.

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/988cccc620dd8c16d77f88ede167b22056176324

Modified Files
--------------
src/backend/catalog/heap.c          |    2 +-
src/backend/catalog/pg_collation.c  |    2 +-
src/backend/catalog/pg_conversion.c |    2 +-
src/backend/catalog/pg_depend.c     |   32 +++++++++++++++++++++++++++++++-
src/backend/catalog/pg_namespace.c  |    2 +-
src/backend/catalog/pg_operator.c   |    2 +-
src/backend/catalog/pg_proc.c       |    6 ++----
src/backend/catalog/pg_type.c       |   11 +++++------
src/backend/commands/foreigncmds.c  |    6 +++---
src/backend/commands/functioncmds.c |   10 +++++-----
src/backend/commands/opclasscmds.c  |    4 ++--
src/backend/commands/proclang.c     |    6 ++----
src/backend/commands/tsearchcmds.c  |    9 ++++-----
src/include/catalog/dependency.h    |    3 ++-
14 files changed, 61 insertions(+), 36 deletions(-)