Add a license to this new file (GPLv2+) so we pass the license check.

(This change needs to be approved Roland Knall--by the file's author--in
Gerrit.)

Change-Id: I58285cb1d773a57fe7d087799bf6d2ffbd962364
Reviewed-on: https://code.wireshark.org/review/3773
Reviewed-by: Roland Knall <rknall@gmail.com>
Reviewed-by: Jeff Morriss <jeff.morriss.ws@gmail.com>