Display Showvolume Audio Channel Names

[bturkus]

Hi, I was wondering if people would be open to tweaking the showvolume filter in "Audio + Video" passthrough mode to display the audio channel names. We could do this in a few other places as well, but I think passthrough in A+V mode would be the most beneficial, as novice vrecord users would not necessarily know that CH1 is stacked on top of CH2 (this just occurred in a Video Preservation class--I knew we were wired improperly, but no one else picked up on it).

@privatezero as I believe you implemented this, what do you think?

Thanks, Ben