Git merges in Moodle 2.5.6 by AMOS bot

commit 035b6840d98e63ea058e20db2451958085caff3c
Author: AMOS bot <amos@moodle.org>
Date:   Wed, 23 Apr 2014 08:38:14 +0800
Tag:    v2.5.6

Merge branch 'MOODLE_25_STABLE' into install_25_STABLE