[ios] - announce support for DTS/AC3 during device enumeration
[ios] - try to set the preferred sample rate on the output device
[ios] - limit iossink to 44100Hz samplerate only - this is the only samplerate that gets realised without conversion as of tests.
[ios] - add float support to the sinewave generator
[ios] - compare the device output samplerate with what we requested (this should match always - 44100Hz - log it if not ...)
[ios] - log errors in checkSessionProperties