the facility has been set, the facility gets set to LOCAL0 and cannot
be changed later.  This seems reasonably plausible to happen, particularly
at higher debug log levels, though I am not certain it explains Han Holl's
recent report.  Easiest fix is to teach the code how to change the value
on-the-fly, which is nicer anyway.  I made the settings PGC_SIGHUP to
conform with log_destination.