PL/Perl: Fix compiler warning

The code was assigning a (Datum) 0 to a void pointer.  That creates a
warning from clang 3.4.  It was probably a thinko to begin with.
Minor improvements to replication slot documentation.

Fix a thinko pointed out by Jeff Davis, and convert a couple of other
references into links.
Remove unnecessary relcache flushes after changing btree metapages.

These flushes were added in my commit d2896a9ed, which added the btree
logic that keeps a cached copy of the index metapage data in index relcache
entries.  The idea was to ensure that other backends would promptly update
their cached copies after a change.  However, this is not really necessary,
since _bt_getroot() has adequate defenses against believing a stale root
page link, and _bt_getrootheight() doesn't have to be 100% right.
Moreover, if it were necessary, a relcache flush would be an unreliable way
to do it, since the sinval mechanism believes that relcache flush requests
represent transactional updates, and therefore discards them on transaction
rollback.  Therefore, we might as well drop these flush requests and save
the time to rebuild the whole relcache entry after a metapage change.

If we ever try to support in-place truncation of btree indexes, it might
be necessary to revisit this issue so that _bt_getroot() can't get caught
by trying to follow a metapage link to a page that no longer exists.
A possible solution to that is to make use of an smgr, rather than
relcache, inval request to force other backends to discard their cached
metapages.  But for the moment this is not worth pursuing.
Fix whitespace
doc: Disable indentation of XHTML output

Indenting the XHTML output can lead to incorrect rendering.  This only
affects the build via XSLT.
Assert(IsTransactionState()) in RelationIdGetRelation().

Commit 42c80c696e9c8323841180029cc62741c21bd356 added an
Assert(IsTransactionState()) in SearchCatCache(), to catch
any code that thought it could do a catcache lookup outside
transactions.  Extend the same idea to relcache lookups.
Alphabeticize list in OBJS definition in utils/adt Makefile.
In RelationClearRelation, postpone cache reload if !IsTransactionState().

We may process relcache flush requests during transaction startup or
shutdown.  In general it's not terribly safe to do catalog access at those
times, so the code's habit of trying to immediately revalidate unflushable
relcache entries is risky.  Although there are no field trouble reports
that are positively traceable to this, we have been able to demonstrate
failure of the assertions recently added in RelationIdGetRelation() and
SearchCatCache().  On the other hand, it seems safe to just postpone
revalidation of the cache entry until we're inside a valid transaction.
The one case where this is questionable is where we're exiting a
subtransaction and the outer transaction is holding the relcache entry open
--- but if we made any significant changes to the rel inside such a
subtransaction, we've got problems anyway.  There are mechanisms in place
to prevent that (to wit, locks for cross-session cases and
CheckTableNotInUse() for intra-session cases), so let's trust to those
mechanisms to keep us out of trouble.
Fix thinko in comment.

Amit Langote
Speed up "rare & frequent" type GIN queries.

If you have a GIN query like "rare & frequent", we currently fetch all the
items that match either rare or frequent, call the consistent function for
each item, and let the consistent function filter out items that only match
one of the terms. However, if we can deduce that "rare" must be present for
the overall qual to be true, we can scan all the rare items, and for each
rare item, skip over to the next frequent item with the same or greater TID.
That greatly speeds up "rare & frequent" type queries.

To implement that, introduce the concept of a tri-state consistent function,
where the 3rd value is MAYBE, indicating that we don't know if that term is
present. Operator classes only provide a boolean consistent function, so we
simulate the tri-state consistent function by calling the boolean function
several times, with the MAYBE arguments set to all combinations of TRUE and
FALSE. Testing all combinations is only feasible for a small number of MAYBE
arguments, but it is envisioned that we'll provide a way for operator
classes to provide a native tri-state consistent function, which can be much
more efficient. But that is not included in this patch.

We were already using that trick to for lossy pages, calling the consistent
function with the lossy entry set to TRUE and FALSE. Now that we have the
tri-state consistent function, use it for lossy pages too.

Alexander Korotkov, with fair amount of refactoring by me.
Initialize the entryRes array between each call to triConsistent.

The shimTriConstistentFn, which calls the opclass's consistent function with
all combinations of TRUE/FALSE for any MAYBE argument, modifies the entryRes
array passed by the caller. Change startScanKey to re-initialize it between
each call to accommodate that.

It's actually a bad habit by shimTriConsistentFn to modify its argument. But
the only caller that doesn't already re-initialize the entryRes array was
startScanKey, and it's easy for startScanKey to do so. Add a comment to
shimTriConsistentFn about that.

Note: this does not give a free pass to opclass-provided consistent
functions to modify the entryRes argument; shimTriConsistent assumes that
they don't, even though it does it itself.

While at it, refactor startScanKey to allocate the requiredEntries and
additionalEntries after it knows exactly how large they need to be. Saves a
little bit of memory, and looks nicer anyway.

Per complaint by Tom Lane, buildfarm and the pg_trgm regression test.
Mark some more variables as static or include the appropriate header

Detected by clang's -Wmissing-variable-declarations.

From: Andres Freund <andres@anarazel.de>
Minor pg_dump improvements

Improve pg_dump by checking results on various fgetc() calls which
previously were unchecked, ditto for ftello.  Also clean up a couple
of very minor memory leaks by waiting to allocate structures until
after the initial check(s).

Issues spotted by Coverity.
Avoid printing uninitialized filename variable in verbose mode

When using verbose mode for pg_basebackup, in tar format sent to
stdout, we'd print an unitialized buffer as the filename.

Reported by Pontus Lundkvist
Limit pg_basebackup progress output to 1/second

This prevents pg_basebackup from generating excessive output when
dumping large clusters. The status is now updated once / second,
still making it possible to see that there is progress happening,
but limiting the total bandwidth.

Mika Eloranta, reviewed by Sawada Masahiko and Oskari Saarenmaa
Focus on ftello result < 0 instead of errno

Rather than reset errno (or just hope that its cleared already),
check just the result of the ftello for < 0 to determine if there
was an issue.

Oversight by me, pointed out by Tom.
Further pg_dump / ftello improvements

Make ftello error-checking consistent to all calls and remove a
bit of ftello-related code which has been #if 0'd out since 2001.

Note that we are not concerned with the ftello() call under
snprintf() failing as it is just building a string to call
exit_horribly() with; printing -1 in such a case is fine.
Use memmove() instead of memcpy() for copying overlapping regions.

In commit d2495f272cd164ff075bee5c4ce95aed11338a36, I fixed this bug in
to_tsquery(), but missed the fact that plainto_tsquery() has the same bug.
Fix WakeupWaiters() to not wake up an exclusive locker unnecessarily.

WakeupWaiters() is supposed to wake up all LW_WAIT_UNTIL_FREE waiters of
the slot, but the loop incorrectly also woke up the first LW_EXCLUSIVE
waiter, if there was no LW_WAIT_UNTIL_FREE waiters in the queue.

Noted by Andres Freund. This code is new in 9.4, so no backpatching.
Don't generate plain-text HISTORY and src/test/regress/README anymore.

Providing this information as plain text was doubtless worth the trouble
ten years ago, but it seems likely that hardly anyone reads it in this
format anymore.  And the effort required to maintain these files (in the
form of extra-complex markup rules in the relevant parts of the SGML
documentation) is significant.  So, let's stop doing that and rely solely
on the other documentation formats.

Per discussion, the plain-text INSTALL instructions might still be worth
their keep, so we continue to generate that file.

Rather than remove HISTORY and src/test/regress/README from distribution
tarballs entirely, replace them with simple stub files that tell the reader
where to find the relevant documentation.  This is mainly to avoid possibly
breaking packaging recipes that expect these files to exist.

Back-patch to all supported branches, because simplifying the markup
requirements for release notes won't help much unless we do it in all
branches.