We have an ilegal hardware instruction in
backend::av_foundation::voices::AVSpeechSynthesisVoice::new(identifier)
when sending voiceWithIdentifier. Is it because the runLoop is not
runing when it's called?
* Fix broken delegate method signature.
* Add `NSRunLoop` into `hello_world` example so delegates are called. Presumably, MacOS apps already run one of these, but the example didn't.
I'd previously attempted to normalize everything to `u8`, but this had some drawbacks:
* It failed to account for some synthesis drivers defining normal as mid-range, while most define it very low.
* It didn't track the normal value for a given synthesizer.
* There was no clean way to map a curve between the minimum, normal, and maximum rates.
Here we track the minimum, normal, and maximum values of rate, pitch, and volume. Sanity checks are done on set.
Also, as a further proof-of-concept, all properties are now implemented for the WinRT driver.
