pgsql: Fix syslogger's rotation disable/re-enable logic.

Fix syslogger's rotation disable/re-enable logic.

If it fails to open a new log file, the syslogger assumes there's something
wrong with its parameters (such as log_directory), and stops attempting
automatic time-based or size-based log file rotations.  Sending it SIGHUP
is supposed to start that up again.  However, the original coding for that
was really bogus, involving clobbering a couple of GUC variables and hoping
that SIGHUP processing would restore them.  Get rid of that technique in
favor of maintaining a separate flag showing we've turned rotation off.
Per report from Mark Kirkwood.

Also, the syslogger will automatically attempt to create the log_directory
directory if it doesn't exist, but that was only happening at startup.
For consistency and ease of use, it should do the same whenever the value
of log_directory is changed by SIGHUP.

Back-patch to all supported branches.

Branch
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REL8_4_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/aa0c797c901d43a5cd7ce74b0348198792c0646b

Modified Files
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src/backend/postmaster/syslogger.c |   26 ++++++++++++++++++++------
1 files changed, 20 insertions(+), 6 deletions(-)