Replace WTFPL with MIT license.

Acked-By: Christophe Massiot <massiot@via.ecp.fr>
Acked-By: Georgi Chorbadzhiyski <gf@unixsol.org>
Acked-By: Jean-Paul Saman <jpsaman@videolan.org>
Acked-By: Rémi Duraffort <ivoire@videolan.org>