Support f64{be,le} PCM formats

[bczhc]

As the title says. Maybe we can have 64-bit floats support, like FFmpeg codec pcm_f64{le,be} and FLOAT64_{LE,BE} in arecord, aplay?

I'm processing some radio IQ data and on the demodulation side, I want to output the raw f64 samples instead of precision-lost f32s, for better extra amplification and further processing to the wav file.

Thanks!