Fix assertion failure by an immediate shutdown.

In PM_WAIT_DEAD_END state, checkpointer process must be dead already.
But an immediate shutdown could make postmaster's state machine
transition to PM_WAIT_DEAD_END state even if checkpointer process is
still running,  and which caused assertion failure. This bug was introduced
in commit 457d6cf049c57cabe9b46ea13f26138040a214ec.

This patch ensures that postmaster's state machine doesn't transition to
PM_WAIT_DEAD_END state in an immediate shutdown while checkpointer
process is running.
Message style improvements
Message punctuation and pluralization fixes
Document how auto_explain.log_timing can be changed.
Docs:  Document to_*() Julian values are integers
Backpatch to 9.3.
Per request from Marc Dahn
docs:  mention Julian is midnight _UTC_
(Yes, there was no UTC back then, but we compute it that way.)
Backpatch to 9.3.
PL/Python: Adjust the regression tests for Python 3.3

Similar to 2cfb1c6f77734db81b6e74bcae630f93b94f69be, the order in which
dictionary elements are printed is not reliable.  This reappeared in the
tests of the string representation of result objects.  Reduce the test
case to one result set column so that there is no question of order.
pg_dump:  avoid schema qualification for ALTER ... OWNER

We already use search_path to specify the schema, so there is no need
for pg_dump to schema-qualify the name.  Also remove dead code.
9.3 release notes:  move foreign table item

Move item about foreign data wrappers supporting inserts/updates/deletes
to object manipulation.

From Etsuro Fujita
Emit a log message if output is about to be redirected away from stderr.

We've seen multiple cases of people looking at the postmaster's original
stderr output to try to diagnose problems, not realizing/remembering that
their logging configuration is set up to send log messages somewhere else.
This seems particularly likely to happen in prepackaged distributions,
since many packagers patch the code to change the factory-standard logging
configuration to something more in line with their platform conventions.

In hopes of reducing confusion, emit a LOG message about this at the point
in startup where we are about to switch log output away from the original
stderr, providing a pointer to where to look instead.  This message will
appear as the last thing in the original stderr output.  (We might later
also try to emit such link messages when logging parameters are changed
on-the-fly; but that case seems to be both noticeably harder to do nicely,
and much less frequently a problem in practice.)

Per discussion, back-patch to 9.3 but not further.