Close #707: Show all messages of the forum if all of them are

Close #707: Show all messages of the forum if all of them are
marked as read.

 Changelog                |    4 ++++
 banana/banana.inc.php.in |   26 +++++++++++++-------------
 banana/spool.inc.php     |   32 ++++++++++++++++++--------------
 3 files changed, 35 insertions(+), 27 deletions(-)

git-svn-id: svn+ssh://murphy/home/svn/banana/trunk@271 9869982d-c50d-0410-be91-f2a2ec7c7c7b