Log a detail message for auth failures due to missing or expired password.

It's worth distinguishing these cases from run-of-the-mill wrong-password
problems, since users have been known to waste lots of time pursuing the
wrong theory about what's failing.  Now, our longstanding policy about how
to report authentication failures is that we don't really want to tell the
*client* such things, since that might be giving information to a bad guy.
But there's nothing wrong with reporting the details to the postmaster log,
and indeed the comments in this area of the code contemplate that
interesting details should be so reported.  We just weren't handling these
particular interesting cases usefully.

To fix, add infrastructure allowing subroutines of ClientAuthentication()
to return a string to be added to the errdetail_log field of the main
authentication-failed error report.  We might later want to use this to
report other subcases of authentication failure the same way, but for the
moment I just dealt with password cases.

Per discussion of a patch from Josh Drake, though this is not what
he proposed.
Revert dup2() checking in syslogger.c

Per the expanded comment-

As we're just trying to reset these to go to DEVNULL, there's not
much point in checking for failure from the close/dup2 calls here,
if they fail then presumably the file descriptors are closed and
any writes will go into the bitbucket anyway.

Pointed out by Tom.
Remove orphaned prototype

Rajeev rastogi
Revert C comment change in slot_attisnull()

Revert 89774b58b0ea2874765cae10c094bb6aaf707feb
Update comment.

generate_normalized_query() no longer needs to truncate text, but this
one comment didn't get the memo.  Per Peter Geoghegan.
Add pg_stat_archiver statistics view.

This view shows the statistics about the WAL archiver process's activity.

Gabriele Bartolini, reviewed by Michael Paquier, refactored a bit by me.
New json functions.

json_build_array() and json_build_object allow for the construction of
arbitrarily complex json trees. json_object() turns a one or two
dimensional array, or two separate arrays, into a json_object of
name/value pairs, similarly to the hstore() function.
json_object_agg() aggregates its two arguments into a single json object
as name value pairs.

Catalog version bumped.

Andrew Dunstan, reviewed by Marko Tiikkaja.
Add new make targets check-tests and installcheck-tests.

These do not run any specific schedule of tests, but only those
specified as part of the invocation, e.g.:

    make check-tests TESTS="json jsonb"
Minor docs fixes for new json functions.

Thom Brown.
Fix compiler warning in EXEC_BACKEND builds.

Per a report by Rajeev Rastogi.
Allow using huge TLB pages on Linux (MAP_HUGETLB)

This patch adds an option, huge_tlb_pages, which allows requesting the
shared memory segment to be allocated using huge pages, by using the
MAP_HUGETLB flag in mmap(). This can improve performance.

The default is 'try', which means that we will attempt using huge pages,
and fall back to non-huge pages if it doesn't work. Currently, only Linux
has MAP_HUGETLB. On other platforms, the default 'try' behaves the same as
'off'.

In the passing, don't try to round the mmap() size to a multiple of
pagesize. mmap() doesn't require that, and there's no particular reason for
PostgreSQL to do that either. When using MAP_HUGETLB, however, round the
request size up to nearest 2MB boundary. This is to work around a bug in
some Linux kernel versions, but also to avoid wasting memory, because the
kernel will round the size up anyway.

Many people were involved in writing this patch, including Christian Kruse,
Richard Poole, Abhijit Menon-Sen, reviewed by Peter Geoghegan, Andres Freund
and me.
Fix docs build.

Broken by the huge_tlb_pages patch.

Vik Fearing.
Remedy two small omissions in the new json functions docs.
Allow skipping some items in a multi-key GIN search.

In a multi-key search, ie. something like "col @> 'foo' AND col @> 'bar'",
as soon as we find the next item that matches the first criteria, we don't
need to check the second criteria for TIDs smaller the first match. That
saves a lot of effort, especially if one of the terms is rare, while the
second occurs very frequently.

Based on ideas from Alexander Korotkov's fast scan patch.
Further optimize multi-key GIN searches.

If we're skipping past a certain TID, avoid decoding posting list segments
that only contain smaller TIDs.

Extracted from Alexander Korotkov's fast scan patch, heavily modified.
Add more C comments to entab.c.
Add C functions to centralize entab processing
Fix pointer processing in new entab.c function
Further optimize GIN multi-key searches.

When skipping over some items in a posting tree, re-find the new location
by descending the tree from root, rather than walking the right links.
This can save a lot of I/O.

Heavily modified from Alexander Korotkov's fast scan patch.
Fix thinko in huge_tlb_pages patch.

We calculated the rounded-up size for the allocation, but then failed to
use the rounded-up value in the mmap() call. Oops.

Also, initialize allocsize, to silence warnings seen with some compilers,
as pointed out by Jeff Janes.