- Patch #13260 by UnConeD: watchdog module improvements.

  We added a 'severity' column to watchdog():
    watchdog($type, $message, $link) --> watchdog($type, $message, $severity, $link);

    * Specify a severity in case you are reporting a warning or error.
    * The $link-parameter is now the fourth parameter instead of the third.

  TODO: document this in the upgrade guide.