fsync backup_label after pg_start_backup()

Dave Kerr
Fix redundant wording
Fix pg_upgrade file share violation on Windows created by the commit
4741e9afb93f0d769655b2d18c2b73b86f281010.  This was done by adding an
optional second log file parameter to exec_prog(), and closing and
reopening the log file between system() calls.

Backpatch to 9.2.
Fix to_char(), to_date(), and to_timestamp() to handle negative/BC
century specifications just like positive/AD centuries.  Previously the
behavior was either wrong or inconsistent with positive/AD handling.

Centuries without years now always assume the first year of the century,
which is now documented.
Fix memory leaks in event trigger code.

Spotted by Jeff Davis.
Tweak new Perl pgindent for compatibility with middle-aged Perls.

We seem to have a rough policy that our Perl scripts should work with
Perl 5.8, so make this one do so.  Main change is to not use the newfangled
\h character class in regexes; "[ \t]" is a serviceable replacement.
Implement SQL-standard LATERAL subqueries.

This patch implements the standard syntax of LATERAL attached to a
sub-SELECT in FROM, and also allows LATERAL attached to a function in FROM,
since set-returning function calls are expected to be one of the principal
use-cases.

The main change here is a rewrite of the mechanism for keeping track of
which relations are visible for column references while the FROM clause is
being scanned.  The parser "namespace" lists are no longer lists of bare
RTEs, but are lists of ParseNamespaceItem structs, which carry an RTE
pointer as well as some visibility-controlling flags.  Aside from
supporting LATERAL correctly, this lets us get rid of the ancient hacks
that required rechecking subqueries and JOIN/ON and function-in-FROM
expressions for invalid references after they were initially parsed.
Invalid column references are now always correctly detected on sight.

In passing, remove assorted parser error checks that are now dead code by
virtue of our having gotten rid of add_missing_from, as well as some
comments that are obsolete for the same reason.  (It was mainly
add_missing_from that caused so much fudging here in the first place.)

The planner support for this feature is very minimal, and will be improved
in future patches.  It works well enough for testing purposes, though.

catversion bump forced due to new field in RangeTblEntry.
Fix TwoPhaseGetDummyBackendId().

This was broken in commit ed0b409d22346b1b027a4c2099ca66984d94b6dd,
which revised the GlobalTransactionData struct to not include the
associated PGPROC as its first member, but overlooked one place where
a cast was used in reliance on that equivalence.

The most effective way of fixing this seems to be to create a new function
that looks up the GlobalTransactionData struct given the XID, and make
both TwoPhaseGetDummyBackendId and TwoPhaseGetDummyProc rely on that.

Per report from Robert Ross.
Update isolation tests' README file.

The directions explaining about running the prepared-transactions test
were not updated in commit ae55d9fbe3871a5e6309d9b91629f1b0ff2b8cba.
Add additional C comments for to_date/to_char() fixes.
Fix cache flush hazard in event trigger cache.

Bug spotted by Jeff Davis using -DCLOBBER_CACHE_ALWAYS.
Fix minor bug in XLogFileRead() that accidentally worked.
Cascading replication copied the incoming file into pg_xlog but
didn't set path correctly, so the first attempt to open file failed
causing it to loop around and look for file in pg_xlog. So the
earlier coding worked, but accidentally rather than by design.

Spotted by Fujii Masao, fix by Fujii Masao and Simon Riggs
Merge parser's p_relnamespace and p_varnamespace lists into a single list.

Now that we are storing structs in these lists, the distinction between
the two lists can be represented with a couple of extra flags while using
only a single list.  This simplifies the code and should save a little
bit of palloc traffic, since the majority of RTEs are represented in both
lists anyway.
Doc correction to point out that 9.2+ can overwrite pg_xlog files.

Noted by Noah Misch, patch by Fujii Masao
Fix typo in comment
Make psql -1 < file behave as expected.

Previously, the -1 option was silently ignored.

Also, emit an error if -1 is used in a context where it won't be
respected, to avoid user confusion.

Original patch by Fabien COELHO, but this version is quite different
from the original submission.
Ensure all replication message info is available and correct via WalRcv
Turn off WalSender keepalives by default, users can enable if desired
Fix upper limit of superuser_reserved_connections, add limit for wal_senders

Should be limited to the maximum number of connections excluding
autovacuum workers, not including.

Add similar check for max_wal_senders, which should never be higher than
max_connections.
Centralize the logic for detecting misplaced aggregates, window funcs, etc.

Formerly we relied on checking after-the-fact to see if an expression
contained aggregates, window functions, or sub-selects when it shouldn't.
This is grotty, easily forgotten (indeed, we had forgotten to teach
DefineIndex about rejecting window functions), and none too efficient
since it requires extra traversals of the parse tree.  To improve matters,
define an enum type that classifies all SQL sub-expressions, store it in
ParseState to show what kind of expression we are currently parsing, and
make transformAggregateCall, transformWindowFuncCall, and transformSubLink
check the expression type and throw error if the type indicates the
construct is disallowed.  This allows removal of a large number of ad-hoc
checks scattered around the code base.  The enum type is sufficiently
fine-grained that we can still produce error messages of at least the
same specificity as before.

Bringing these error checks together revealed that we'd been none too
consistent about phrasing of the error messages, so standardize the wording
a bit.

Also, rewrite checking of aggregate arguments so that it requires only one
traversal of the arguments, rather than up to three as before.

In passing, clean up some more comments left over from add_missing_from
support, and annotate some tests that I think are dead code now that that's
gone.  (I didn't risk actually removing said dead code, though.)