[bugfix] DISCARD ALL does not release advisory locks

It was brought to my attention that DISCARD ALL
does not release advisory locks:

  http://pgfoundry.org/tracker/index.php?func=detail&aid=1010499&group_id=1000258&atid=983

Thus connection managers / poolers need to do that manually.

This obviously means DISCARD ALL needs fixing.  Applied
patch adds LockReleaseAll(USER_LOCKMETHOD, true) call
to DiscardAll().

Should this also be fixed in 8.3?

--
marko