Git commits in Moodle 2.7.13 by Eloy Lafuente (stronk7)

commit 8459a1e0c9ed1cab31ddcadd2af202ba60a305ce
Author: Eloy Lafuente (stronk7) <stronk7@moodle.org>
Date:   Sat, 06 Feb 2016 19:12:35 +0800
Tag:    v2.7.13

MDL-51580 environment: 3.1 requirements added