Move PGAC_LDAP_SAFE to config/programs.m4.

This restores the style of keeping configure.in free of AC_DEFUN.  Per
gripe from Tom Lane.
Handle WAIT_IO_COMPLETION return from WaitForMultipleObjectsEx().

This return code is possible wherever we pass bAlertable = TRUE; it
arises when Windows caused the current thread to run an "I/O completion
routine" or an "asynchronous procedure call".  PostgreSQL does not
provoke either of those Windows facilities, hence this bug remaining
largely unnoticed, but other local code might do so.  Due to a shortage
of complaints, no back-patch for now.

Per report from Shiv Shivaraju Gowda, this bug can cause
PGSemaphoreLock() to PANIC.  The bug can also cause select() to report
timeout expiration too early, which might confuse pgstat_init() and
CheckRADIUSAuth().
Fix a performance problem in pg_dump's dump order selection logic.

findDependencyLoops() was not bright about cases where there are multiple
dependency paths between the same two dumpable objects.  In most scenarios
this did not hurt us too badly; but since the introduction of section
boundary pseudo-objects in commit a1ef01fe163b304760088e3e30eb22036910a495,
it was possible for this code to take unreasonable amounts of time (tens
of seconds on a database with a couple thousand objects), as reported in
bug #11033 from Joe Van Dyk.  Joe's particular problem scenario involved
"pg_dump -a" mode with long chains of foreign key constraints, but I think
that similar problems could arise with other situations as long as there
were enough objects.  To fix, add a flag array that lets us notice when we
arrive at the same object again while searching from a given start object.
This simple change seems to be enough to eliminate the performance problem.

Back-patch to 9.1, like the patch that introduced section boundary objects.
doc: Fix up ALTER TABLESPACE reference page

The documentation of ALTER TABLESPACE ... MOVE was added without any
markup, not even paragraph breaks.  Fix that, and clarify the text in a
few places.