WASAPI: Handle AUDCLNT_E_DEVICE_IN_USE

[Sin-tel]

Small fix: changes the backend-specific error from a cryptic "0x8889000A" to "The device is already in use.".

[roderickvd]

Hmm. I'm not sure about the custom string. Why not have it also return DeviceNotAvailable?

[Sin-tel]

Currently docs say that DeviceNotAvailable means e.g. the device is literally unplugged. In my use-case I want to display something helpful like "Another application is using this device." to the user.

[roderickvd]

You could argue that it's another kind of "not available". If important to discern between the two then we could consider returning a variant, or heck, even consider some kind of std::io::Error.

[roderickvd]

Thanks, merged!