libdiscid update from 0.2.2 to 0.6.1
chromaprint: switch FFT implementation to ffmpeg, build fpcalc

FFmpeg is prefered over FFTW3, and a mutual dependency of picard and acoustid-fingerprinter
picard: fix libdisc and acoustid fingerprinting issues

fpcalc is the external fingerprinter, not acoustid-fingerprinter