Author: Petr Škoda
MDL-41115 fix username field label when allowing login via email
Thanks Marina for spotting this!
http://git.moodle.org/gw?p=moodle.git;a=commit;h=b7679cdbfbb22af9d363456d86b7d617c2b343e4
http://github.com/moodle/moodle/commit/b7679cdbfbb22af9d363456d86b7d617c2b343e4
+ 2.7 en [usernameemail,core]