Fix concat() and format() to handle VARIADIC-labeled arguments correctly.

Previously, the VARIADIC labeling was effectively ignored, but now these
functions act as though the array elements had all been given as separate
arguments.

Pavel Stehule
Make pg_dump exclude unlogged table data on hot standby slaves

Noted by Joe Van Dyk
Add some randomness to the choice of which GiST page to insert to.

When descending the tree for an insert, and there are multiple equally good
pages we could insert to, make the choice in random. Previously, we would
always choose the tuple with lowest offset number. That meant that when two
non-leaf pages overlap - in the extreme case they might have exactly the same
key - all but the first such page went unused. That wasn't optimal for space
usage; if you deleted some tuples from the non-first pages, the space would
never be reused.

With this patch, the other pages are sometimes chosen too, although there's
still a heavy bias towards low-offset tuples, so that we don't lose cache
locality when doing a lot of inserts with similar keys.

Original idea by Alexander Korotkov, although this patch version was written
by me and copy-edited by Tom Lane.
doc:  improve wording of "foreign data server" in file-fdw docs

Backpatch to 9.2

Shigeru HANADA
Add prosecdef to \df+ output.

Jon Erdman, reviewed by Phil Sorber and Stephen Frost.
docs:  In ecpg, clarify how username/password colon parameters are used

Backpatch to 9.2.

Patch from Alan B
Make it easy to time out pg_isready, and make the default 3 seconds.

Along the way, add a missing line to the help message.

Phil Sorber, reviewed by Fujii Masao
doc:  split search_path index entries into separate secondaries

Karl O. Pinc
doc:  adjust search_path secondary index mention

per Tom Lane
doc:  merge ecpg username/password example into C comment

Backpatch to 9.2

per Tom Lane
Change plan caching to honor, not resist, changes in search_path.

In the initial implementation of plan caching, we saved the active
search_path when a plan was first cached, then reinstalled that path
anytime we needed to reparse or replan.  The idea of that was to try to
reselect the same referenced objects, in somewhat the same way that views
continue to refer to the same objects in the face of schema or name
changes.  Of course, that analogy doesn't bear close inspection, since
holding the search_path fixed doesn't cope with object drops or renames.
Moreover sticking with the old path seems to create more surprises than
it avoids.  So instead of doing that, consider that the cached plan depends
on search_path, and force reparse/replan if the active search_path is
different than it was when we last saved the plan.

This gets us fairly close to having "transparency" of plan caching, in the
sense that the cached statement acts the same as if you'd just resubmitted
the original query text for another execution.  There are still some corner
cases where this fails though: a new object added in the search path
schema(s) might capture a reference in the query text, but we'd not realize
that and force a reparse.  We might try to fix that in the future, but for
the moment it looks too expensive and complicated.
doc: mention commit_delay is only honored if fsync is enabled

per Tianyin Xu
WIP for MVs: Eliminate unnecessary duplication of function.

per report from Noah Misch
Merge branch 'master' of /home/kgrittn/pg/postgresql into matview