Git commits in Moodle 3.6.0 by Markku Riekkinen

commit a776169ee9b973fdccd6c7c41b212e701344bb63
Author: Markku Riekkinen <markku.riekkinen@aalto.fi>
Date:   Thu, 20 Sep 2018 20:00:52 +0800
Tag:    v3.6.0-beta

MDL-61981 filter_mathjaxloader: add unit tests

commit 194ffa2344455145f7dd4bf71bd1173aff1407ff
Author: Markku Riekkinen <markku.riekkinen@aalto.fi>
Date:   Wed, 19 Sep 2018 17:04:23 +0800
Tag:    v3.6.0-beta

MDL-61981 filter_mathjaxloader: nested math environments