IFF ANIM: fix decoding of ANIM-1

[ami_stuff]

found one more sample

C:\>ffmpeg -i HBHill.anim out.avi
ffmpeg version 3.0.git Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.6.2 (GCC)
  configuration: --disable-pthreads --enable-gpl --disable-ffprobe
  libavutil      55. 24.100 / 55. 24.100
  libavcodec     57. 40.100 / 57. 40.100
  libavformat    57. 36.100 / 57. 36.100
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 45.100 /  6. 45.100
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
[iff @ 021ad160] Warning: not compiled with thread support, using thread emulati
on
Input #0, iff, from 'HBHill.anim':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: iff_ilbm (ANIM / 0x4D494E41), pal8, 320x400, SAR 20:11 D
AR 16:11, 60 fps, 60 tbr, 60 tbn
[iff @ 02538060] Warning: not compiled with thread support, using thread emulati
on
[mpeg4 @ 021a5640] Warning: not compiled with thread support, using thread emula
tion
[avi @ 021a4720] Using AVStream.codec to pass codec parameters to muxers is depr
ecated, use AVStream.codecpar instead.
Output #0, avi, to 'out.avi':
  Metadata:
    ISFT            : Lavf57.36.100
    Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 320x400 [SAR 20:11 D
AR 16:11], q=2-31, 200 kb/s, 60 fps, 60 tbn
    Metadata:
      encoder         : Lavc57.40.100 mpeg4
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
Stream mapping:
  Stream #0:0 -> #0:0 (iff_ilbm (iff) -> mpeg4 (native))
Press [q] to stop, [?] for help
frame=   26 fps=0.0 q=31.0 Lsize=     129kB time=00:00:00.58 bitrate=1808.3kbits
/s speed=18.7x
video:122kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing o
verhead: 5.284254%

[ami_stuff]

decodes correctly with ShowANIM from:

​http://aminet.net/package/docs/misc/IFFSpecs

[Elon Musk]

Fixed in 17ea1cd55960851f2e3e637ddf7fc5d35086a452.