Git commits in Moodle 2.7.15 by Marina Glancy

commit 80c861c1fea15b0666ddcc0c1f2b4f42e21b49bf
Author: Marina Glancy <marina@moodle.com>
Date:   Mon, 04 Jul 2016 10:32:20 +0800
Tag:    v2.7.15

MDL-55069 core: escape special characters in email headers