avcodec: Add bits_per_raw_sample to AVCodecParameters

The bits_per_raw_sample represents the number of bits of precision per sample.

The field is added at the logical place, not at the end as the code was just
recently added

This fixes the regression about losing the audio sample precision information

The change in the fate test checksum un-does the change from the merge

Previous version reviewed by: wm4 <nfxjfg@googlemail.com>
Previous version reviewed by: Dominik 'Rathann' Mierzejewski <dominik@greysector.net>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
