Port override skeleton for ffmpeg

[justin at shiningsilence.com]

>
> 	Hi,
>
> 	The FreeBSD port for ffmpeg does not compile because of the moved
> bktr and meteor header files. I've placed a DragonFly port override for
> it at ftp://ftp.sohara.org/pub/ffmpeg.tar.gz.

I assume you mean ftp://ftp.sohara.org/pub/ffmpeg.tgz ?

It worked, or at least the program printed a helpful usage message and
exited when I built it using the override.  It does the same thing when I
don't have the override, though - should it?