This abandons the combo box approach an instead partially reverts to the popup.
We now display a suffix after the stream title saying " on <device>" or " from <device>"
where the <device> part looks like a hyperlink and, when clicked, shows the popup to change the device.
If there is only one device available, we suppress the whole thing and thus avoid confusion.
This makes the default button work on sinks/sources, allows the drop
down to actually change the sink/source and removes the old menu code.
Some names and such are fixed in the glade file too.
Colin Guthrie