Git commits in Moodle x.x.x by Arjen Lentz

commit 4b71e99564fa8d40e25bbf5de387fc37f8fcf8ca
Author: Arjen Lentz <arjenlentz@catalyst-au.net>
Date:   Mon, 18 Feb 2019 09:30:32 +0800
Tag:    v3.7.0-beta

MDL-21475 weblib: Simplify validate_email() to use existing function.