add my copyright as well

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@16900 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavformat/mxfenc.c

 /*
  * MXF muxer
  * Copyright (c) 2008 GUCAS, Zhentan Feng <spyfeng at gmail dot com>
+ * Copyright (c) 2008 Baptiste Coudurier <baptiste dot coudurier at gmail dot com>
  *
  * This file is part of FFmpeg.
  *