This changes the Q value of the chain of second order low-pass filters
making up the high order filters. Previously the Q value was always set
to 0.707107 for the entire chain, but this is incorrect for Butterworth
filters when the order is greater than 2.

This should make a small improvement to the quality of the linear
resampler.

This is in preparation for improving ma_lpf, ma_hpf and ma_bpf to make
them proper Butterworth filters.

This API is called ma_peak.

This API is called ma_encoder. Currently it only supports encoding to
WAV files, which is done via dr_wav.