Git commits in Moodle 3.6.6 by Nicolas Dunand

commit 029c0fdb8521aca184e208ee4cc3020c66e3d909
Author: Nicolas Dunand <nico@kolya.ch>
Date:   Wed, 26 Sep 2018 14:50:10 +0800
Tag:    v3.6.6

MDL-63458 core_user: Remove send message if messaging is disabled