Fix possible crash with nested SubLinks.

An expression such as WHERE (... x IN (SELECT ...) ...) IN (SELECT ...)
could produce an invalid plan that results in a crash at execution time,
if the planner attempts to flatten the outer IN into a semi-join.
This happens because convert_testexpr() was not expecting any nested
SubLinks and would wrongly replace any PARAM_SUBLINK Params belonging
to the inner SubLink.  (I think the comment denying that this case could
happen was wrong when written; it's certainly been wrong for quite a long
time, since very early versions of the semijoin flattening logic.)

Per report from Teodor Sigaev.  Back-patch to all supported branches.
Tweak placement of explicit ANALYZE commands in the regression tests.

Make the COPY test, which loads most of the large static tables used in
the tests, also explicitly ANALYZE those tables.  This allows us to get
rid of various ad-hoc, and rather redundant, ANALYZE commands that had
gotten stuck into various test scripts over time to ensure we got
consistent plan choices.  (We could have done a database-wide ANALYZE,
but that would cause stats to get attached to the small static tables
too, which results in plan changes compared to the historical behavior.
I'm not sure that's a good idea, so not going that far for now.)

Back-patch to 9.0, since 9.0 and 9.1 are currently sometimes failing
regression tests for lack of an "ANALYZE tenk1" in the subselect test.
There's no need for this in 8.4 since we didn't print any plans back
then.
Fix ancient docs/comments thinko: XID comparison is mod 2^32, not 2^31.

Pointed out by Gianni Ciolli.
Add HOLD/RESUME_INTERRUPTS in HandleCatchupInterrupt/HandleNotifyInterrupt.

This prevents a possible longjmp out of the signal handler if a timeout
or SIGINT occurs while something within the handler has transiently set
ImmediateInterruptOK.  For safety we must hold off the timeout or cancel
error until we're back in mainline, or at least till we reach the end of
the signal handler when ImmediateInterruptOK was true at entry.  This
syncs these functions with the logic now present in handle_sig_alarm.

AFAICT there is no live bug here in 9.0 and up, because I don't think we
currently can wait for any heavyweight lock inside these functions, and
there is no other code (except read-from-client) that will turn on
ImmediateInterruptOK.  However, that was not true pre-9.0: in older
branches ProcessIncomingNotify might block trying to lock pg_listener, and
then a SIGINT could lead to undesirable control flow.  It might be all
right anyway given the relatively narrow code ranges in which NOTIFY
interrupts are enabled, but for safety's sake I'm back-patching this.
Fix inherited UPDATE/DELETE with UNION ALL subqueries.

Fix an oversight in commit b3aaf9081a1a95c245fd605dcf02c91b3a5c3a29: we do
indeed need to process the planner's append_rel_list when copying RTE
subqueries, because if any of them were flattenable UNION ALL subqueries,
the append_rel_list shows which subquery RTEs were pulled up out of which
other ones.  Without this, UNION ALL subqueries aren't correctly inserted
into the update plans for inheritance child tables after the first one,
typically resulting in no update happening for those child table(s).
Per report from Victor Yegorov.

Experimentation with this case also exposed a fault in commit
a7b965382cf0cb30aeacb112572718045e6d4be7: if an inherited UPDATE/DELETE
was proven totally dummy by constraint exclusion, we might arrive at
add_rtes_to_flat_rtable with root->simple_rel_array being NULL.  This
should be interpreted as not having any RelOptInfos.  I chose to code
the guard as a check against simple_rel_array_size, so as to also
provide some protection against indexing off the end of the array.

Back-patch to 9.2 where the faulty code was added.
Add "SHIFT_JIS" as an accepted encoding name for locale checking.

When locale is "ja_JP.SJIS", nl_langinfo(CODESET) returns "SHIFT_JIS"
on some platforms, at least on RedHat Linux. So the encoding/locale
match table (encoding_match_list) needs the entry. Otherwise client
encoding is set to SQL_ASCII.

Back patch to all supported branches.