This is done in preparation for some documentation generation and also
to get it out of the way of the part of the documentation that explains
how to use the library.

This is useful for those only using miniaudio for data conversion,
decoding and/or encoding.

Public issue https://github.com/dr-soft/miniaudio/issues/171

Public issue https://github.com/dr-soft/miniaudio/issues/171

Public issue https://github.com/dr-soft/miniaudio/issues/171

Public issue https://github.com/dr-soft/miniaudio/issues/172

I've noticed that a lot of this doesn't actually require atomic
operations so this may be reviewed again later.

This fixes an issue where a decoding backend can report configurations
outside of miniaudio's limits.

Public issues:
  * https://github.com/dr-soft/miniaudio/issues/166
  * https://github.com/dr-soft/miniaudio/issues/167

This is uninitializing the ring buffer before the device which results
in a situation where a stray data callback may try touching the buffer
after it's be uninitialized.

This is an internal change and does not affect any public APIs. This
change is in preparation for future lock-free high level APIs.