Git commits in Moodle 3.2.x by Helson Castro

commit 8ea5d72218c663afbe206ec5bed27070021963e6
Author: Helson Castro <helsonaraujo@hotmail.com>
Date:   Fri, 27 Jan 2017 13:55:07 +0800
Tag:    v3.2.2

MDL-57568 forms: Added missing include for button element.