add license header to blacklist file

Change-Id: I19edaf928ab4d99b5d3c399b59e26d515c2265b0
Reviewed-on: https://gerrit.libreoffice.org/16333Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>

vcl/opengl/opengl_blacklist_windows.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+* This file is part of the LibreOffice project.
+*
+* This Source Code Form is subject to the terms of the Mozilla Public
+* License, v. 2.0. If a copy of the MPL was not distributed with this
+* file, You can obtain one at http://mozilla.org/MPL/2.0/.
+-->
 <root>
     <whitelist>
         <entry os="7" vendor="intel" compare="equal" version="10.18.10.3412">