avcodec/rawdec: for 16-bit pix fmts, shift pixels when bits_per_coded_sample < 16

Signed-off-by: Peter Ross <pross@xvid.org>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
libswscale: bayer to rgb24 & yv12 colorspace converters

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>