largeobject regression tests - updated patch

Given the recent changes to the regression scripts, the large object
regression test patch I submitted quite a while ago, and is currently in
the patch hold queue, no longer cleanly applies.  This patch is
functionally the same as the last one, but cleanly applies to current CVS
head.

Note that this patch requires the psql largeobject quiet mode patch which
is also in the hold queue and still applies cleanly.