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

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@21935 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

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.