[Discuss-gnuradio] Demo Audio Code

[Matthew Ettus]

I have checked in working GrAudioSource and GrAudioSink files.  They now handle
1 or 2 streams each.  OSS sound drivers split multichannel cards into separate
stereo devices, so this doesn't stop you from working with >2 channels.  You'll
just need multiple GrAudioXXX blocks.

ALSA handles multichannel cards much better, so it will need to be integrated in
order to do this right.

The source and sink now also handle scaling for you, and both work with
VrComplex data.

There is demo code --
    See full_duplex_audio_demo.cc in the src/gnu/examples directory for an
example of single channel, 16-bit data I/O, full_duplex.
    See complex_audio_fft.cc in the same directory for an example of Complex
I/O, also full duplex.  This one will do a complex FFT on the stereo input,
assuming the Left channel is real, and the right channel is imaginary.  Joesph
-- this is the one I promised you.

Let me know if you have trouble

Matt