Fix Session::registerLogoutHandler to set the dirty flag.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@606 44740490-163a-0410-bde0-09ae8108e29a

lib/SimpleSAML/Session.php

@@ -463,6 +463,7 @@ class SimpleSAML_Session {
 	 */
 	public function registerLogoutHandler($file, $classname, $functionname) {
 		$this->logout_handlers[] = array('file' => $file, 'class' => $classname, 'function' => $functionname);
+		$this->dirty = TRUE;
 	}