Git commits in Moodle 2.9.3 by Jetha Chan

commit ee7300f6e6c7ec6684fe2e8dc1c136c308b3df1f
Author: Jetha Chan <jetha@moodle.com>
Date:   Thu, 02 Jul 2015 10:19:50 +0800
Tag:    v2.9.3

MDL-50685 core_form: disable hidden options, don't just hide