Replace the implementation of the audio device with portaudio or libsoundio

[portaudio](https://portaudio.com/) is an audio I/O library that has better support for some functionalities and is lighter-weight than SDL2. It also includes ASIO implementation. But it does not support hot-plug detection.
[libsoundio](http://libsound.io/) is another audio I/O library that supports hot-plug detection.