Git merges in Moodle 2.1.8 by AMOS bot

commit 9865cbfb6073f2b55331c8a8093d8e67bd920d99
Author: AMOS bot <amos@moodle.org>
Date:   Sat, 08 Sep 2012 08:34:49 +0800
Tag:    v2.1.8

Merge branch 'MOODLE_21_STABLE' into install_21_STABLE