Allow suppressing publication of posted messages according to rejection reason

Allow suppressing publication of posted messages according to rejection reason

This is done by creating
  BASEDIR/settings.publish-rejection-kinds
with a series of lines of the form
  [!]<glob-pattern>
where <glob-pattern> may contain * and ? and matches the short
rejection reason keyword.  First match wins; ! means do not publish;
if file does not exist or we run off the end, we do publish.

All of this depends on PUBLISHREJECTIONS=true in settings.