uaudio MFCs to 4.x

[Julian Elischer]

I have just merged a set of changes from current to RELENG_4 for usb audio.

USB audio in 4.x was not terribly well supported anyhow, but if you are 
running
RELENG_4 and have a usb audio output device (input may not work,  yet) 
you might
 like to do a  "before and after" test.    I have limited USB audio 
output equipment,
and it didn't work on a lot of devices prior to these changes but I'd 
like to
hear if it got worse

:-)