Log PortAudio unanticipated host errors

Print the full error message for unanticipated host errors.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Automatically choose sample rate

Until now we assumed that audio devices support 48 kHz sampling rate.
Some devices only support 44.1 kHz or other weird rates.  Automatically
pick the best sampling rate.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Print audio configuration to log

Make troubleshooting easier by printing details of the audio
configuration to the log.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>