pgsql: Allow LOCK TABLE .. ROW EXCLUSIVE MODE with INSERT

Allow LOCK TABLE .. ROW EXCLUSIVE MODE with INSERT

INSERT acquires RowExclusiveLock during normal operation and therefore
it makes sense to allow LOCK TABLE .. ROW EXCLUSIVE MODE to be executed
by users who have INSERT rights on a table (even if they don't have
UPDATE or DELETE).

Not back-patching this as it's a behavior change which, strictly
speaking, loosens security restrictions.

Per discussion with Tom and Robert (circa 2013).

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/fa2642438f189c2b169ace3ac1df19533b9c7781

Modified Files
--------------
doc/src/sgml/ref/lock.sgml | 8 +++++---
src/backend/commands/lockcmds.c | 12 ++++++++----
2 files changed, 13 insertions(+), 7 deletions(-)