Do not use an empty hostname.

When trying to connect to a given database libecpg should not try using an
empty hostname if no hostname was given.
Rename walLogHints to wal_log_hints for easier grepping.

Michael Paquier
Fix contrib/pg_upgrade to clean all the cruft made during "make check".

Although these files get cleaned up if the test runs to completion,
a failure partway through leaves trash all over the floor.  The Makefile
ought to be bright enough to get rid of it when you say "make clean".
Aggressively freeze tables when CLUSTER or VACUUM FULL rewrites them.

We haven't wanted to do this in the past on the grounds that in rare
cases the original xmin value will be needed for forensic purposes, but
commit 37484ad2aacef5ec794f4dd3d5cf814475180a78 removes that objection,
so now we can.

Per extensive discussion, among many people, on pgsql-hackers.
Handle wraparound during truncation in multixact/members

In pg_multixact/members, relying on modulo-2^32 arithmetic for
wraparound handling doesn't work all that well.  Because we don't
explicitely track wraparound of the allocation counter for members, it
is possible that the "live" area exceeds 2^31 entries; trying to remove
SLRU segments that are "old" according to the original logic might lead
to removal of segments still in use.  To fix, have the truncation
routine use a tailored SlruScanDirectory callback that keeps track of
the live area in actual use; that way, when the live range exceeds 2^31
entries, the oldest segments still live will not get removed untimely.

This new SlruScanDir callback needs to take care not to remove segments
that are "in the future": if new SLRU segments appear while the
truncation is ongoing, make sure we don't remove them.  This requires
examination of shared memory state to recheck for false positives, but
testing suggests that this doesn't cause a problem.  The original coding
didn't suffer from this pitfall because segments created when truncation
is running are never considered to be removable.

Per Andres Freund's investigation of bug #8673 reported by Serge
Negodyuck.
Wrap multixact/members correctly during extension

In the 9.2 code for extending multixact/members, the logic was very
simple because the number of entries in a members page was a proper
divisor of 2^32, and thus at 2^32 wraparound the logic for page switch
was identical than at any other page boundary.  In commit 0ac5ad5134f I
failed to realize this and introduced code that was not able to go over
the 2^32 boundary.  Fix that by ensuring that when we reach the last
page of the last segment we correctly zero the initial page of the
initial segment, using correct uint32-wraparound-safe arithmetic.

Noticed while investigating bug #8673 reported by Serge Negodyuck, as
diagnosed by Andres Freund.
Handle 5-char filenames in SlruScanDirectory

Original users of slru.c were all producing 4-digit filenames, so that
was all that that code was prepared to handle.  Changes to multixact.c
in the course of commit 0ac5ad5134f made pg_multixact/members create
5-digit filenames once a certain threshold was reached, which
SlruScanDirectory wasn't prepared to deal with; in particular,
5-digit-name files were not removed during truncation.  Change that
routine to make it aware of those files, and have it process them just
like any others.

Right now, some pg_multixact/members directories will contain a mixture
of 4-char and 5-char filenames.  A future commit is expected fix things
so that each slru.c user declares the correct maximum width for the
files it produces, to avoid such unsightly mixtures.

Noticed while investigating bug #8673 reported by Serge Negodyuck.
Fix calculation of maximum statistics-message size.

The PGSTAT_NUM_TABENTRIES macro should have been updated when new fields
were added to struct PgStat_MsgTabstat in commit 644828908, but it wasn't.
Fix that.

Also, add a static assertion that we didn't overrun the intended size limit
on stats messages.  This will not necessarily catch every mistake in
computing the maximum array size for stats messages, but it will catch ones
that have practical consequences.  (The assertion in fact doesn't complain
about the aforementioned error in PGSTAT_NUM_TABENTRIES, because that was
not big enough to cause the array length to increase.)

No back-patch, as there's no actual bug in existing releases; this is just
in the nature of future-proofing.

Mark Dilger and Tom Lane
Ooops, should use double not single quotes in StaticAssertStmt().

That's what I get for testing this on an older compiler.