Git merges in Moodle 2.5.3 by AMOS bot

commit caf0834e405f660d8d8eb79a258507517e4ba26d
Author: AMOS bot <amos@moodle.org>
Date:   Sat, 14 Sep 2013 08:41:35 +0800
Tag:    v2.5.3

Merge branch 'MOODLE_25_STABLE' into install_25_STABLE