Add proper LGPL header.

Originally committed as revision 5634 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavutil/md5.c

 /*
  * Copyright (C) 2006 Michael Niedermayer (michaelni@gmx.at)
  * Copyright (C) 2003-2005 by Christopher R. Hertel (crh@ubiqx.mn.org)
- * #inlcude LGPL license
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  *
  * References:
  *  IETF RFC 1321: The MD5 Message-Digest Algorithm