Update the licensing info following the instructions at
http://www.w3.org/Consortium/Legal/2008/04-testsuite-copyright.html#howtouse

Fixes golang/go#10398.

Change-Id: Ib37b2a696a5287f41d4e85da4eb7ec1cbb346301
Reviewed-on: https://go-review.googlesource.com/8978Reviewed-by: Martin Packman <martin.packman@canonical.com>
Reviewed-by: Rob Pike <r@golang.org>