Git commits in Moodle 3.5.3 by Markku Riekkinen

commit e4099493cac84b3dfc60cba2d9adbc53a011826e
Author: Markku Riekkinen <markku.riekkinen@aalto.fi>
Date:   Thu, 20 Sep 2018 20:00:52 +0800
Tag:    v3.5.3

MDL-61981 filter_mathjaxloader: add unit tests

commit 71d3c750eb56bd2ee2c853269143b6672c3600fb
Author: Markku Riekkinen <markku.riekkinen@aalto.fi>
Date:   Wed, 19 Sep 2018 17:04:23 +0800
Tag:    v3.5.3

MDL-61981 filter_mathjaxloader: nested math environments