pgsql: Add DISCARD SEQUENCES command.

Add DISCARD SEQUENCES command.

DISCARD ALL will now discard cached sequence information, as well.

Fabrízio de Royes Mello, reviewed by Zoltán Böszörményi, with some
further tweaks by me.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/d90ced8bb22194cbb45f58beb0961251103aeff5

Modified Files
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doc/src/sgml/ref/discard.sgml          |   12 +++++++++++-
src/backend/commands/discard.c         |    8 +++++++-
src/backend/commands/sequence.c        |   16 ++++++++++++++++
src/backend/parser/gram.y              |    9 ++++++++-
src/backend/tcop/utility.c             |    3 +++
src/bin/psql/tab-complete.c            |    2 +-
src/include/commands/sequence.h        |    1 +
src/include/nodes/parsenodes.h         |    1 +
src/test/regress/expected/sequence.out |    3 +++
src/test/regress/sql/sequence.sql      |    2 ++
10 files changed, 53 insertions(+), 4 deletions(-)