* SET CHANNEL AUDIO_OUTPUT_TYPE <chan> <driver> command is back!
creates an audio output device instance of the given driver type
('Jack' or 'Alsa') with default parameters if none exists,
otherwise it just picks the first available device and assign
it to the intended sampler channel.
* The AudioOutputDevice class get's a new pure virtual method,
Driver(), which is implemented on both of the existing inherited
classes, AudioOutputDeviceAlsa and AudioOutputDeviceJack, with
the sole purpose to return the driver type name as a String
('Alsa' and 'Jack', respectively).
* The quoting on the filename argument for the LOAD INSTRUMENT
command has been made optional; you can have both ways, with
single quotes or none, keeping compability with older LSCP
* An additional sanity check is made on LOAD INSTRUMENT, whether
the sampler channel has an audio output device assigned, thus
preventing the server from crashing on instrument file load.
* The GET AUDIO_OUTPUT_DEVICE INFO now includes the missing
'driver' item, as predicted by the draft protocol document.