* Introducing new UI for grabbing.

      There's an option -grab <format> that basically acts as -i
      but for grabbing. So now it's possible to grab from multiple
      sources at once and fully control -r -s and -pix_fmt for
      each individual grab.

    * removing -dv1394
      Please use -grab dv1394 instead.

Originally committed as revision 3613 to svn://svn.ffmpeg.org/ffmpeg/trunk