add support for IFF YAFA

[ami_stuff]

​http://aminet.net/package/docs/misc/YAFA-doc

plays with:

​http://www.morguesoft.eu/Contenido/Programs/Windows/AWC-WIN.zip

C:\>d:\ffmpeg -i C:\1\yafa_none_2\raw_8bpp_delta_none_post_none.yafa
ffmpeg version N-80270-gd4cd8e7 Copyright (c) 2000-2016 the FFmpeg developers
  built with gcc 4.5.0 (GCC) 20100414 (Fedora MinGW 4.5.0-1.fc14)
  configuration: --prefix=/var/www/users/research/ffmpeg/snapshots/build --arch=
x86 --target-os=mingw32 --cross-prefix=i686-pc-mingw32- --cc='ccache i686-pc-min
gw32-gcc' --enable-pthreads --enable-memalign-hack --enable-runtime-cpudetect --
enable-cross-compile --enable-static --disable-shared --extra-libs='-lws2_32 -lw
inmm -lpthread' --extra-cflags='--static -I/var/www/users/research/ffmpeg/snapsh
ots/build/include' --extra-ldflags='-static -L/var/www/users/research/ffmpeg/sna
pshots/build/lib' --enable-bzlib --enable-zlib --enable-gpl --enable-version3 --
enable-nonfree --enable-libx264 --enable-libspeex --enable-libtheora --enable-li
bvorbis --enable-libfaac --enable-libxvid --enable-libopencore-amrnb --enable-li
bopencore-amrwb --enable-libmp3lame --enable-libfreetype --enable-libvpx --disab
le-decoder=libvpx
  libavutil      55. 24.100 / 55. 24.100
  libavcodec     57. 46.100 / 57. 46.100
  libavformat    57. 37.101 / 57. 37.101
  libavdevice    57.  0.101 / 57.  0.101
  libavfilter     6. 46.101 /  6. 46.101
  libswscale      4.  1.100 /  4.  1.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
C:\1\yafa_none_2\raw_8bpp_delta_none_post_none.yafa: Invalid data found when pro
cessing input

[ami_stuff]

forgot about samples:

​https://www.datafilehost.com/d/98b50828

[ami_stuff]

samples:

​https://samples.ffmpeg.org/ffmpeg-bugs/trac/ticket5632/

[ami_stuff]

This IFF ANIM/YAFA player works fine on linux, good for debugging:

​https://github.com/BlitterStudio/AnimPlayer/releases