Git commits in Moodle 3.4.4 by David Mudrák

commit 644a76167ab5de7681f521e45dcf14fa1ab627c9
Author: David Mudrák <david@moodle.com>
Date:   Mon, 18 Jun 2018 23:58:39 +0800
Tag:    v3.4.4

MDL-62621 comments: Add missing indexes on comments table