replace FIR with finite differences. 3x faster decode_subframe_fixed(). overall flac decoding: 10% faster if file was encoded with fixed predictors.
replace FIR with finite differences.
3x faster decode_subframe_fixed().
overall flac decoding: 10% faster if file was encoded with fixed predictors.


git-svn-id: a4d7c1866f8397a4106e0b57fc4fbf792bbdaaaf@10626 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg