Git commits in Moodle 3.5.4 by Leon Stringer

commit 43246bd859817a02e1fb527a392ef412cad566d8
Author: Leon Stringer <leon.stringer@ntlworld.com>
Date:   Wed, 12 Dec 2018 01:22:59 +0800
Tag:    v3.5.4

MDL-58596 core_stats: fixed infinite loop cause by DST change