All audio module source and sink constructors are now homologous.
They accept:
audio.sink(sample_rate, device_name, ok_to_block),
audio.source(sample_rate, device_name, ok_to_block),
where device_name and ok_to_block are optional and default to "" and
True respectively. ok_to_block should be False when there's another
source or sink in the flow graph that's really setting the pacing
through the pipeline. Note that at this time, only the
audio_portaudio implementation pays attention to ok_to_block. All
others treat it as if it were True.