ljpeg: support 64bpp rgba

[ami_stuff]

​http://www1.datafilehost.com/d/3475e370

C:\>ffmpeg -i 64bpp_rgba_lossless.jpg out.bmp
ffmpeg version N-56277-g2fcef19 Copyright (c) 2000-2013 the FFmpeg developers
  built on Sep 15 2013 02:23:39 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      52. 43.100 / 52. 43.100
  libavcodec     55. 31.101 / 55. 31.101
  libavformat    55. 16.102 / 55. 16.102
  libavdevice    55.  3.100 / 55.  3.100
  libavfilter     3. 84.100 /  3. 84.100
  libswscale      2.  5.100 /  2.  5.100
  libswresample   0. 17.103 /  0. 17.103
  libpostproc    52.  3.100 / 52.  3.100
[image2 @ 0x205fa40] Stream #0: not enough frames to estimate rate; consider inc
reasing probesize
Input #0, image2, from '64bpp_rgba_lossless.jpg':
  Duration: 00:00:00.04, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: mjpeg, abgr, 1200x1200, 25 tbr, 25 tbn, 25 tbc
Output #0, image2, to 'out.bmp':
  Metadata:
    encoder         : Lavf55.16.102
    Stream #0:0: Video: bmp, bgra, 1200x1200, q=2-31, 200 kb/s, 90k tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg -> bmp)
Press [q] to stop, [?] for help
frame=    1 fps=0.0 q=-1.0 Lsize=N/A time=00:00:00.04 bitrate=N/A
video:5625kB audio:0kB subtitle:0 global headers:0kB muxing overhead -100.000382
%

[Michael Niedermayer]

Fixed in 1e4e0bd907ebf4e69af84276f789f304f52a280f and 7fb2622456b9c43b96b2a1e64a3aeb13281ce3de