Fix compute_scalar_stats() for case that all values exceed WIDTH_THRESHOLD.

The standard typanalyze functions skip over values whose detoasted size
exceeds WIDTH_THRESHOLD (1024 bytes), so as to limit memory bloat during
ANALYZE.  However, we (I think I, actually :-() failed to consider the
possibility that *every* non-null value in a column is too wide.  While
compute_minimal_stats() seems to behave reasonably anyway in such a case,
compute_scalar_stats() just fell through and generated no pg_statistic
entry at all.  That's unnecessarily pessimistic: we can still produce
valid stanullfrac and stawidth values in such cases, since we do include
too-wide values in the average-width calculation.  Furthermore, since the
general assumption in this code is that too-wide values are probably all
distinct from each other, it seems reasonable to set stadistinct to -1
("all distinct").

Per complaint from Kadri Raudsepp.  This has been like this since roughly
neolithic times, so back-patch to all supported branches.
Fix possible crashes due to using elog/ereport too early in startup.

Per reports from Andres Freund and Luke Campbell, a server failure during
set_pglocale_pgservice results in a segfault rather than a useful error
message, because the infrastructure needed to use ereport hasn't been
initialized; specifically, MemoryContextInit hasn't been called.
One known cause of this is starting the server in a directory it
doesn't have permission to read.

We could try to prevent set_pglocale_pgservice from using anything that
depends on palloc or elog, but that would be messy, and the odds of future
breakage seem high.  Moreover there are other things being called in main.c
that look likely to use palloc or elog too --- perhaps those things
shouldn't be there, but they are there today.  The best solution seems to
be to move the call of MemoryContextInit to very early in the backend's
real main() function.  I've verified that an elog or ereport occurring
immediately after that is now capable of sending something useful to
stderr.

I also added code to elog.c to print something intelligible rather than
just crashing if MemoryContextInit hasn't created the ErrorContext.
This could happen if MemoryContextInit itself fails (due to malloc
failure), and provides some future-proofing against someone trying to
sneak in new code even earlier in server startup.

Back-patch to all supported branches.  Since we've only heard reports of
this type of failure recently, it may be that some recent change has made
it more likely to see a crash of this kind; but it sure looks like it's
broken all the way back.
Fix calculation of ISMN check digit.

This has always been broken, so back-patch to all supported versions.

Fabien COELHO
Fix possible buffer overrun in contrib/pg_trgm.

Allow for the possibility that folding a string to lower case makes it
longer (due to replacing a character with a longer multibyte character).
This doesn't change the number of trigrams that will be extracted, but
it does affect the required size of an intermediate buffer in
generate_trgm().  Per bug #8821 from Ufuk Kayserilioglu.

Also install some checks that the input string length is not so large
as to cause overflow in the calculations of palloc request sizes.

Back-patch to all supported versions.
Fix client-only installation

The psql Makefile was not creating $(datadir) before installing
psqlrc.sample there.

In most cases, the directory would be created in some other way, but for
the documented from-source client-only installation procedure, it could
fail.

Reported-by: Mike Blackwell <mike.blackwell@rrd.com>
Allow SET TABLESPACE to database default

We've always allowed CREATE TABLE to create tables in the database's default
tablespace without checking for CREATE permissions on that tablespace.
Unfortunately, the original implementation of ALTER TABLE ... SET TABLESPACE
didn't pick up on that exception.

This changes ALTER TABLE ... SET TABLESPACE to allow the database's default
tablespace without checking for CREATE rights on that tablespace, just as
CREATE TABLE works today.  Users could always do this through a series of
commands (CREATE TABLE ... AS SELECT * FROM ...; DROP TABLE ...; etc), so
let's fix the oversight in SET TABLESPACE's original implementation.