[osx/coreaudio] - add method for fetching the the start channel number of a stream in relation to its owner device
[osx/coreaudio] - add method for setting the audio source of a device, and methods for fetching audio sources and their names, constify where needed
[AE/osxsink] - for the extra display name use the audiosource name or the channel numbers for multistream devices
[AE/osxsink] - for the default device show the devicename behind it as extraname
[AE/osxsink] - enumerate the audio sources of a device if there are any - this allows to select between multiple airplay sinks for example
- obey the streamidx during initialize/streamscoring