Code review for protransform patches.

Fix loss of previous expression-simplification work when a transform
function fires: we must not simply revert to untransformed input tree.
Instead build a dummy FuncExpr node to pass to the transform function.
This has the additional advantage of providing a simpler, more uniform
API for transform functions.

Move documentation to a somewhat less buried spot, relocate some
poorly-placed code, be more wary of null constants and invalid typmod
values, add an opr_sanity check on protransform function signatures,
and some other minor cosmetic adjustments.

Note: although this patch touches pg_proc.h, no need for catversion
bump, because the changes are cosmetic and don't actually change the
intended catalog contents.
Refactor simplify_function et al to centralize argument simplification.

We were doing the recursive simplification of function/operator arguments
in half a dozen different places, with rather baroque logic to ensure it
didn't get done multiple times on some arguments.  This patch improves that
by postponing argument simplification until after we've dealt with named
parameters and added any needed default expressions.

Marti Raudsepp, somewhat hacked on by me
Cast some printf arguments to avoid possibly-nonportable behavior.

Per compiler warnings on buildfarm member black_firefly.
Fix planner's handling of outer PlaceHolderVars within subqueries.

For some reason, in the original coding of the PlaceHolderVar mechanism
I had supposed that PlaceHolderVars couldn't propagate into subqueries.
That is of course entirely possible.  When it happens, we need to treat
an outer-level PlaceHolderVar much like an outer Var or Aggref, that is
SS_replace_correlation_vars() needs to replace the PlaceHolderVar with
a Param, and then when building the finished SubPlan we have to provide
the PlaceHolderVar expression as an actual parameter for the SubPlan.
The handling of the contained expression is a bit delicate but it can be
treated exactly like an Aggref's expression.

In addition to the missing logic in subselect.c, prepjointree.c was failing
to search subqueries for PlaceHolderVars that need their relids adjusted
during subquery pullup.  It looks like everyplace else that touches
PlaceHolderVars got it right, though.

Per report from Mark Murawski.  In 9.1 and HEAD, queries affected by this
oversight would fail with "ERROR: Upper-level PlaceHolderVar found where
not expected".  But in 9.0 and 8.4, you'd silently get possibly-wrong
answers, since the value transmitted into the subquery wouldn't go to null
when it should.
Replace empty locale name with implied value in CREATE DATABASE and initdb.

setlocale() accepts locale name "" as meaning "the locale specified by the
process's environment variables".  Historically we've accepted that for
Postgres' locale settings, too.  However, it's fairly unsafe to store an
empty string in a new database's pg_database.datcollate or datctype fields,
because then the interpretation could vary across postmaster restarts,
possibly resulting in index corruption and other unpleasantness.

Instead, we should expand "" to whatever it means at the moment of calling
CREATE DATABASE, which we can do by saving the value returned by
setlocale().

For consistency, make initdb set up the initial lc_xxx parameter values the
same way.  initdb was already doing the right thing for empty locale names,
but it did not replace non-empty names with setlocale results.  On a
platform where setlocale chooses to canonicalize the spellings of locale
names, this would result in annoying inconsistency.  (It seems that popular
implementations of setlocale don't do such canonicalization, which is a
pity, but the POSIX spec certainly allows it to be done.)  The same risk
of inconsistency leads me to not venture back-patching this, although it
could certainly be seen as a longstanding bug.

Per report from Jeff Davis, though this is not his proposed patch.
Fix COPY FROM for null marker strings that correspond to invalid encoding.

The COPY documentation says "COPY FROM matches the input against the null
string before removing backslashes".  It is therefore reasonable to presume
that null markers like E'\\0' will work ... and they did, until someone put
the tests in the wrong order during microoptimization-driven rewrites.
Since then, we've been failing if the null marker is something that would
de-escape to an invalidly-encoded string.  Since null markers generally
need to be something that can't appear in the data, this represents a
nontrivial loss of functionality; surprising nobody noticed it earlier.

Per report from Jeff Davis.  Backpatch to 8.4 where this got broken.
Code cleanup for heap_freeze_tuple.

It used to be case that lazy vacuum could call this function with only
a shared lock on the buffer, but neither lazy vacuum nor any other
code path does that any more.  Simplify the code accordingly and clean
up some related, obsolete comments.
Remove dead assignment

found by Coverity
Improve PL/Python database access function documentation

Organize the function descriptions as a list instead of running text,
for easier access.
pg_dump: Small message adjustment for consistency
Silence compiler warning about uninitialized variable.
New GUC, track_iotiming, to track I/O timings.

Currently, the only way to see the numbers this gathers is via
EXPLAIN (ANALYZE, BUFFERS), but the plan is to add visibility through
the stats collector and pg_stat_statements in subsequent patches.

Ants Aasma, reviewed by Greg Smith, with some further changes by me.
Add some infrastructure for contrib/pg_stat_statements.

Add a queryId field to Query and PlannedStmt.  This is not used by the
core backend, except for being copied around at appropriate times.
It's meant to allow plug-ins to track a particular query forward from
parse analysis to execution.

The queryId is intentionally not dumped into stored rules (and hence this
commit doesn't bump catversion).  You could argue that choice either way,
but it seems better that stored rule strings not have any dependency
on plug-ins that might or might not be present.

Also, add a post_parse_analyze_hook that gets invoked at the end of
parse analysis (but only for top-level analysis of complete queries,
not cases such as analyzing a domain's default-value expression).
This is mainly meant to be used to compute and assign a queryId,
but it could have other applications.

Peter Geoghegan
Bend parse location rules for the convenience of pg_stat_statements.

Generally, the parse location assigned to a multiple-token construct is
the location of its leftmost token.  This commit breaks that rule for
the syntaxes TYPENAME 'LITERAL' and CAST(CONSTANT AS TYPENAME) --- the
resulting Const will have the location of the literal string, not the
typename or CAST keyword.  The cases where this matters are pretty thin on
the ground (no error messages in the regression tests change, for example),
and it's unlikely that any user would be confused anyway by an error cursor
pointing at the literal.  But still it's less than consistent.  The reason
for changing it is that contrib/pg_stat_statements wants to know the parse
location of the original literal, and it was agreed that this is the least
unpleasant way to preserve that information through parse analysis.

Peter Geoghegan
Expose track_iotiming information via pg_stat_statements.

Ants Aasma, reviewed by Greg Smith, with very minor tweaks by me.
pg_test_timing utility, to measure clock monotonicity and timing cost.

Ants Aasma, Greg Smith
Doc fix for pg_test_timing.

Fujii Masao
pg_basebackup: Error message improvements.

Fujii Masao
pg_basebackup: Error handling fixes.

Thomas Ogrisegg and Fujii Masao
Attempt to unbreak pg_test_timing on Windows.

Per buildfarm, and Álvaro Herrera.