Add regression test for bug fixed by recent refactoring.

Test case by Andres Freund for bug fixed by Tom Lane's refactoring
in commit 5194024d72f33fb209e10f9ab0ada7cc67df45b7
Fix permission tests for views/tables proven empty by constraint exclusion.

A view defined as "select <something> where false" had the curious property
that the system wouldn't check whether users had the privileges necessary
to select from it.  More generally, permissions checks could be skipped
for tables referenced in sub-selects or views that were proven empty by
constraint exclusion (although some quick testing suggests this seldom
happens in cases of practical interest).  This happened because the planner
failed to include rangetable entries for such tables in the finished plan.

This was noticed in connection with erroneous handling of materialized
views, but actually the issue is quite unrelated to matviews.  Therefore,
revert commit 200ba1667b3a8d7a9d559d2f05f83d209c9d8267 in favor of a more
direct test for the real problem.

Back-patch to 9.2 where the bug was introduced (by commit
7741dd6590073719688891898e85f0cb73453159).
Use correct length to convert json unicode escapes.

Bug reported on IRC - fix due to Andrew Gierth.
pg_test_fsync: update output to show usecs/op clearer
Prevent (auto)vacuum from truncating first page of populated matview.

Per report from Fujii Masao, with regression test using his example.
9.3 release notes:  suggested improvements from Jeff Janes and Josh Berkus
9.3 release notes:  update for current commits

Also, remove broken link in release.sgml.
Improve SPI documentation about null-flags arrays.

Clarify the description of nulls[] arguments, and use the same wording
for all SPI functions with this type of argument.  Per gripe from Yuriy
Rusinov.
9.3 release notes:  add markup for text

Still need to add links for new features.
9.3 release notes:  Add links to SGML sections
9.3 release notes:  Add markup for pg_backup_start_time()
9.3 release notes:  move compatibility items into their own section
9.3 release notes:  adjustments

Fixes from Peter Geoghegan, Ian Lawrence Barwick, Marti Raudsepp
docs:  fix log_line_prefix session id docs

Backpatch to 9.2.

Report from Ian Lawrence Barwick
9.3 docs:  wording fixes

From Erik Rijkers
docs:  log_line_prefix session id fix

Restore 4-byte designation for docs.  Fix 9.3 doc query to properly pad
to four digits.

Backpatch to all active branches

Per suggestions from Ian Lawrence Barwick
docs:  Improve log_line_prefix session_id query
Improve behavior of \watch with non-tuple-returning commands.

Print the command tag if we get PGRES_COMMAND_OK, and throw an error for
other cases.  Per gripe from Michael Paquier.

In passing, add an fflush(), just to be real sure the output appears
before we sleep.
Translation updates
Revert idea of zer-padding padding session id in log_line_prefix

Removal of doc adjustment and release note mention as well.