iff: support IFF ACBM with byterun1 compression

[ami_stuff]

C:\>ffmpeg -i 0900.acbm out.bmp
ffmpeg version N-78758-g5156578 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 5.3.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
le-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --
enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-l
ibilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enab
le-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --en
able-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --ena
ble-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --
enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-lib
x265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-d
ecklink --enable-zlib
  libavutil      55. 19.100 / 55. 19.100
  libavcodec     57. 27.100 / 57. 27.100
  libavformat    57. 26.100 / 57. 26.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 37.100 /  6. 37.100
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Input #0, iff, from '0900.acbm':
  Metadata:
    comment         : $VER: Written by ASDG's Art Department Professional IFF3.0
.1 (09.04.92)
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: iff_ilbm (ACBM / 0x4D424341), rgb0, 124x511, SAR 20:11 D
AR 2480:5621, 90k tbr, 90k tbn, 90k tbc
[image2 @ 038fcfe0] Frame rate very high for a muxer not efficiently supporting
it.
Please consider specifying a lower framerate, a different muxer or -vsync 2
Output #0, image2, to 'out.bmp':
  Metadata:
    comment         : $VER: Written by ASDG's Art Department Professional IFF3.0
.1 (09.04.92)
    encoder         : Lavf57.26.100
    Stream #0:0: Video: bmp, bgr24, 124x511 [SAR 20:11 DAR 2480:5621], q=2-31, 2
00 kb/s, 90k fps, 90k tbn, 90k tbc
    Metadata:
      encoder         : Lavc57.27.100 bmp
Stream mapping:
  Stream #0:0 -> #0:0 (iff_ilbm (iff) -> bmp (native))
Press [q] to stop, [?] for help
frame=    1 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.00 bitrate=N/A speed=0.000704
x
video:186kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing o
verhead: unknown

[Elon Musk]

Fixed in 5979fb0b1ec3637dc1ce26313eb89bf009923fb0.