Various changes to AC3->IEC958 framer. Mostly to make our IEC958 headers and dump...

Various changes to AC3->IEC958 framer. Mostly to make our IEC958 headers and dump the frame (as a probable sync failu...

Original commit message from CVS:
Various changes to AC3->IEC958 framer. Mostly to make our IEC958 headers
more accurate, and to check AC3 checksums (both of them in each frame),
and dump the frame (as a probable sync failure) if they don't match.
General code cleanup, improved comments. Changed to not construct the
header backwards, and not byteswap everything else. If we end up needing
to do little-endian output, we should swap in the element doing the
output (AC3 is big-endian).