license: liblangtag is LGPLv3+/MPLv2

See: http://tagoh.github.io/liblangtag/#sec2
or
workdir/UnpackedTarball/liblangtag/README

Change-Id: I0ce9b4c6ada0dad93f214d23f43800b89b6533df
Reviewed-on: https://gerrit.libreoffice.org/69497
Tested-by: Jenkins
Reviewed-by: Andras Timar <andras.timar@collabora.com>

readlicense_oo/license/license.xml

@@ -706,6 +706,7 @@
         <p>The following software may be included in this product: liblangtag. Use of any of this software is governed
         by the terms of the license below:</p>
         <p><a href="#a__LGPL_version_3">Jump to LGPL Version 3</a></p>
+        <p><a href="#a__MPL_version_2">Jump to MPL Version 2.0</a></p>
     </div>
     <div class="MSPUB">
         <h2>libmspub</h2>