add support for Brodway MPEG codec (BW10)

[ami_stuff]

​http://samples.multimedia.cx/V-codecs/BW10/cartonfold.avi

​http://xanim.polter.net/files/xanim2801.tar.gz

seems to be supported by xanim:

xa_mpg.c:
  /* Check for Broadway MPEG encoding(BW10)
   * Skip 12 bytes and then expect GOP
   */
  if (extra & 0x01)
  { MPG_FLUSH_BBITS(32);
    MPG_FLUSH_BBITS(32);
    MPG_FLUSH_BBITS(32);
    qtab = xmpg_def_intra_qtab;
  }
  else if (extra & 0x02)  /* XING Editable MPEG */
  {
    qtab = xmpg_def_intra_qtab;
  }

  vert_pos = -1;

C:\>ffmpeg -i C:\cartonfold.avi
FFmpeg version git-N-29181-ga304071, Copyright (c) 2000-2011 the FFmpeg develope
rs
  built on Apr 18 2011 21:24:03 with gcc 4.5.2
  configuration: --enable-gpl --enable-version3 --enable-runtime-cpudetect --ena
ble-memalign-hack --enable-avisynth --enable-bzlib --enable-frei0r --enable-libo
pencore-amrnb --enable-libopencore-amrwb --enable-libfreetype --enable-libgsm --
enable-libmp3lame --enable-libopenjpeg --enable-librtmp --enable-libschroedinger
 --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libvpx --enabl
e-libx264 --enable-libxavs --enable-libxvid --enable-zlib --cross-prefix=i686-w6
4-mingw32- --target-os=mingw32 --arch=x86_32 --extra-cflags=-I/home/kyle/softwar
e/ffmpeg/external-libraries/win32/include --extra-ldflags=-L/home/kyle/software/
ffmpeg/external-libraries/win32/lib --pkg-config=pkg-config
  libavutil    50. 40. 1 / 50. 40. 1
  libavcodec   52.120. 0 / 52.120. 0
  libavformat  52.108. 0 / 52.108. 0
  libavdevice  52.  4. 0 / 52.  4. 0
  libavfilter   1. 79. 0 /  1. 79. 0
  libswscale    0. 13. 0 /  0. 13. 0
[avi @ 01CEC000] max_analyze_duration reached
Input #0, avi, from 'C:\cartonfold.avi':
  Metadata:
    creation_time   : 2003-06-14 1:06:14
  Duration: 00:02:20.44, start: 0.000000, bitrate: 292 kb/s
    Stream #0.0: Video: BW10 / 0x30315742, 352x288, 25 fps, 25 tbr, 25 tbn, 25 t
bc
    Stream #0.1: Audio: pcm_s16le, 44100 Hz, 2 channels, s16, 1411 kb/s
At least one output file must be specified

[Carl Eugen Hoyos]

Fixed by Michael.