Git commits in Moodle 3.5.7 by Bas Brands

commit 7a548abf0115f6beb8f0bf82327af9430c8e6b29
Author: Bas Brands <bas@moodle.com>
Date:   Mon, 13 May 2019 18:29:48 +0800
Tag:    v3.5.7

MDL-65581 core_blocks: change classname for hidden blocks