more fail-safe FLAC parser

I submitted my FLAC parser (as mentioned in my last post) to the ffmpeg-devel mailing list and got a suggestion (a.k.a. requirement) from Michael for decreasing the likelihood of false-positive frame detection. Basically it would analyze a sequence of potential frame headers and pick the most likely sub-sequence based on concurrent non-overlapping CRC matches. It would also take header parameter changes into account. I am currently working on an implementation of this idea.