add EM4A fourcc , works for: http://av.watch.impress.co.jp/docs/20040929/xf.asf
add EM4A fourcc , works for:
http://av.watch.impress.co.jp/docs/20040929/xf.asf


git-svn-id: a4d7c1866f8397a4106e0b57fc4fbf792bbdaaaf@16729 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg