chkpass:  check for NULL return value from crypt()

Report from Jozef Mlich using Coverity
doc: mention statistics reset during crash recovery

Takayuki Tsunakawa
Clear MyProc and MyProcSignalState before they become invalid.

Evidence from buildfarm member crake suggests that the new test_shm_mq
module is routinely crashing the server due to the arrival of a SIGUSR1
after the shared memory segment has been unmapped.  Although processes
using the new dynamic background worker facilities are more likely to
receive a SIGUSR1 around this time, the problem is also possible on older
branches, so I'm back-patching the parts of this change that apply to
older branches as far as they apply.

It's already generally the case that code checks whether these pointers
are NULL before deferencing them, so the important thing is mostly to
make sure that they do get set to NULL before they become invalid.  But
in master, there's one case in procsignal_sigusr1_handler that lacks a
NULL guard, so add that.

Patch by me; review by Tom Lane.
pg_restore:  make help output plural for multi-enabled options

per report from Josh Kupershmidt
docs:  mention 'g' is not in the regex embedded options table

Mentioned in substring() and regexp_replace() sections.
Introduce replication slots.

Replication slots are a crash-safe data structure which can be created
on either a master or a standby to prevent premature removal of
write-ahead log segments needed by a standby, as well as (with
hot_standby_feedback=on) pruning of tuples whose removal would cause
replication conflicts.  Slots have some advantages over existing
techniques, as explained in the documentation.

In a few places, we refer to the type of replication slots introduced
by this patch as "physical" slots, because forthcoming patches for
logical decoding will also have slots, but with somewhat different
properties.

Andres Freund and Robert Haas
arrays:  tighten checks for multi-dimensional input

Previously an input array string that started with a single-element
array dimension would then later accept a multi-dimensional segment.

BACKWARD INCOMPATIBILITY
Copy the libpq DLL to the bin directory on Mingw and Cygwin.

This has long been done by the MSVC build system, and has caused
confusion in the past when programs like psql have failed to start
because they can't find the DLL. If it's in the same directory as it now
will be they will find it.

Backpatch to all live branches.
Don't use deprecated dllwrap on Cygwin.

The preferred method is to use "cc -shared", and this allows binaries
to be rebased if required, unlike dllwrap.

Backpatch to 9.0 where we have buildfarm coverage.

There are still some issues with Cygwin, especially modern Cygwin, but
this helps us get closer to good support.

Marco Atzeri.
Fix some more bugs in signal handlers and process shutdown logic.

WalSndKill was doing things exactly backwards: it should first clear
MyWalSnd (to stop signal handlers from touching MyWalSnd->latch),
then disown the latch, and only then mark the WalSnd struct unused by
clearing its pid field.

Also, WalRcvSigUsr1Handler and worker_spi_sighup failed to preserve
errno, which is surely a requirement for any signal handler.

Per discussion of recent buildfarm failures.  Back-patch as far
as the relevant code exists.
fix whitespace
Fix some wide-character bugs in the text-search parser.

In p_isdigit and other character class test functions generated by the
p_iswhat macro, the code path for non-C locales with multibyte encodings
contained a bogus pointer cast that would accidentally fail to malfunction
if types wchar_t and wint_t have the same width.  Apparently that is true
on most platforms, but not on recent Cygwin releases.  Remove the cast,
as it seems completely unnecessary (I think it arose from a false analogy
to the need to cast to unsigned char when dealing with the <ctype.h>
functions).  Per bug #8970 from Marco Atzeri.

In the same functions, the code path for C locale with a multibyte encoding
simply ANDed each wide character with 0xFF before passing it to the
corresponding <ctype.h> function.  This could result in false positive
answers for some non-ASCII characters, so use a range test instead.
Noted by me while investigating Marco's complaint.

Also, remove some useless though not actually buggy maskings and casts
in the hand-coded p_isalnum and p_isalpha functions, which evidently
got tested a bit more carefully than the macro-generated functions.
Fix makefile syntax.