Git merges in Moodle 2.3.9 by AMOS bot

commit b47ef00098136052c7dc7f075b0260a3d0e8c251
Author: AMOS bot <amos@moodle.org>
Date:   Sat, 27 Jul 2013 08:43:15 +0800
Tag:    v2.3.9

Merge branch 'MOODLE_23_STABLE' into install_23_STABLE