[dev] new function for Notification.php

[steve]

I added a new function for horde/lib/Notification.php to remove a listener 
not needed any more.

diff -w -b -r1.29 Notification.php
106a107,122
 > 	 * Remove a listener from the notification list
 >     * @param string $driver          The name of the listener to attach.
 >     */
 >     function unattach($listener)
 >     {
 >         $listener = String::lower(basename($listener));
 >         if (!array_key_exists($listener, $this->_listeners)) {
 >             Horde::fatal(PEAR::raiseError(sprintf(_("Notification 
listener %s not found."), $listener)), __FILE__, __LINE__);
 >         }
 >
 >         unset($this->_listeners[$listener]);
 >         unset($_SESSION['hordeMessageStacks'][$listener]);
 > 		return;
 >     }
 >
 >     /**
138a155
 >