Dynamic noise reduction capability via speex (or opus)

[markjfine]

With conditions as sporadic as they've been, thinking it might be helpful to add dynamic noise reduction via speex or opus codecs. Both are free, open, and I believe available on all platforms. I can see another row of controls underneath the current Noise blanker, with a label 'DNR', a text/spinner combo similar to Squelch in order to adjust the the level from -1 to -96 dB, and a button to (dis)engage it.

Throwing this idea for a new feature out there, as I've piped GQRX output through DReaM's AM Demodulator to get the same effect. Although a clunky way to accomplish this, it does work pretty well.