Use the official FFmpeg spelling: "ffmpeg" -> "FFmpeg".

Originally committed as revision 21935 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffplay.c

 /*
- * FFplay : Simple Media Player based on the ffmpeg libraries
+ * FFplay : Simple Media Player based on the FFmpeg libraries
  * Copyright (c) 2003 Fabrice Bellard
  *
  * This file is part of FFmpeg.