[PATCH] Implement (and document, and test) has_sequence_privilege()

That this family of functions did not exist earlier was merely an
oversight.

Signed-off-by: Abhijit Menon-Sen <ams@oryx.com>
---
 doc/src/sgml/func.sgml                   |   28 ++++
 src/backend/utils/adt/acl.c              |  210 ++++++++++++++++++++++++++++++
 src/include/catalog/pg_proc.h            |   13 ++
 src/include/utils/builtins.h             |    6 +
 src/test/regress/expected/privileges.out |   22 +++
 src/test/regress/sql/privileges.sql      |   17 +++
 6 files changed, 296 insertions(+), 0 deletions(-)