Git merges in Moodle 2.6.4 by Daniel Neis Araujo

commit 3414e35610ef4531da94cbbf18132da86661bbc5
Author: Daniel Neis Araujo <danielneis@gmail.com>
Date:   Mon, 12 May 2014 23:18:51 +0800
Tag:    v2.6.4

Merge remote-tracking branch 'moodle/MOODLE_26_STABLE' into MOODLE_26_STABLE