pgsql: Allow a user to kill his own queries using pg_cancel_backend()

Allow a user to kill his own queries using pg_cancel_backend()

Allows a user to use pg_cancel_queries() to cancel queries in
other backends if they are running under the same role.
pg_terminate_backend() still requires superuser permissoins.

Short patch, many authors working on the bikeshed: Magnus Hagander,
Josh Kupershmidt, Edward Muller, Greg Smith.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/0495aaad8b337642830a4d4e82f8b8c02b27b1be

Modified Files
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doc/src/sgml/func.sgml | 13 +++++--
src/backend/utils/adt/misc.c | 80 ++++++++++++++++++++++++++++++++++++-----
2 files changed, 80 insertions(+), 13 deletions(-)