pgsql: Create new errcode for recovery conflict caused by db drop on ma

Create new errcode for recovery conflict caused by db drop on master.
Previously reported as ERRCODE_ADMIN_SHUTDOWN, this case is now
reported as ERRCODE_DATABASE_DROPPED. No message text change.
Unlikely to happen on most servers, so low impact change to allow
session poolers to correctly handle this situation.

Tatsuo Ishii and Simon Riggs

Branch
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REL9_0_STABLE

Details
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http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=d6c1dc176a422ed19d698bb8ff9ed7b38c04a320

Modified Files
--------------
doc/src/sgml/errcodes.sgml      |    6 ++++++
src/backend/tcop/postgres.c     |    2 +-
src/include/utils/errcodes.h    |    1 +
src/pl/plpgsql/src/plerrcodes.h |    4 ++++
4 files changed, 12 insertions(+), 1 deletions(-)