Author: Peter Burnett
MDL-68820 web: Added referrer policy header setting
http://git.moodle.org/gw?p=moodle.git;a=commit;h=b4623c8975682b6c01468e776266f1f484e42a1c
http://github.com/moodle/moodle/commit/b4623c8975682b6c01468e776266f1f484e42a1c
+ 4.0 en [referrernone,core_admin]
+ 4.0 en [referrerpolicy,core_admin]
+ 4.0 en [referrerpolicydesc,core_admin]