Git commits in Moodle 3.1.5 by Adrian Greeve

commit 9634c940d4ae249d2b7fa80967c12238103d6ac7
Author: Adrian Greeve <adrian@moodle.com>
Date:   Thu, 09 Feb 2017 09:20:38 +0800
Tag:    v3.1.5

MDL-51833 tool_monitor: Improve access check for monitor.

commit 39e019735f312aadf0030ca1ae4fcc3980c3c661
Author: Adrian Greeve <adrian@moodle.com>
Date:   Tue, 10 Jan 2017 14:50:35 +0800
Tag:    v3.1.5

MDL-48228 database: Make utf8mb4 the default character set for mysql.

commit fb1fcfb4f3478af12e09f4591c5587c4a6342b36
Author: Adrian Greeve <adrian@moodle.com>
Date:   Tue, 10 Jan 2017 14:50:18 +0800
Tag:    v3.1.5

MDL-48228 database: Unit test addition and update.