mov enc: fix gray8 in mov

[ami_stuff]

Curently gray8 rawvideo exported to mov is decoded incorrectly by qt because qt expect bits_per_coded_sample to be set to 0x28 and not 0x08 as it is now.

Attached patch fixes this problem, but there is still another issue - gray8 is decoded in negative by qt.

C:\>ffmpeg -i 160.bmp -vcodec rawvideo -pix_fmt gray out.mov
ffmpeg version N-47325-gb90e795 Copyright (c) 2000-2012 the FFmpeg developers
  built on Dec  1 2012 02:23:25 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-w32threads --enable-memalign-hack --enable-runtime-cpudetect
--enable-cross-compile --enable-static --disable-shared --extra-libs='-lws2_32 -
lwinmm -lpthread' --extra-cflags='--static -I/var/www/users/research/ffmpeg/snap
shots/build/include' --extra-ldflags='-static -L/var/www/users/research/ffmpeg/s
napshots/build/lib' --enable-bzlib --enable-zlib --enable-gpl --enable-version3
--enable-nonfree --enable-libx264 --enable-libspeex --enable-libtheora --enable-
libvorbis --enable-libfaac --enable-libxvid --enable-libopencore-amrnb --enable-
libopencore-amrwb --enable-libmp3lame --enable-libvpx --disable-decoder=libvpx
  libavutil      52. 10.100 / 52. 10.100
  libavcodec     54. 78.100 / 54. 78.100
  libavformat    54. 41.100 / 54. 41.100
  libavdevice    54.  3.101 / 54.  3.101
  libavfilter     3. 23.104 /  3. 23.104
  libswscale      2.  1.103 /  2.  1.103
  libswresample   0. 17.101 /  0. 17.101
  libpostproc    52.  2.100 / 52.  2.100
Input #0, image2, from '160.bmp':
  Duration: 00:00:00.04, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: bmp, bgr24, 160x120, 25 tbr, 25 tbn, 25 tbc
Output #0, mov, to 'out.mov':
  Metadata:
    encoder         : Lavf54.41.100
    Stream #0:0: Video: rawvideo (raw  / 0x20776172), gray, 160x120, q=2-31, 200
 kb/s, 12800 tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (bmp -> rawvideo)
Press [q] to stop, [?] for help
frame=    1 fps=0.0 q=0.0 Lsize=      19kB time=00:00:00.04 bitrate=3985.2kbits/
s
video:19kB audio:0kB subtitle:0 global headers:0kB muxing overhead 3.781250%

[Carl Eugen Hoyos]

Fixed by an unrelated change in 9a2778082121ea44d06a2f00f822ea99109c7fd8