This was causing issues for me on WASAPI where it would return an error
indicating that the device was already in use: AUDCLNT_E_DEVICE_IN_USE.

If this is a bug in mini_al I'm happy to re-enable this once it's
fixed, but I've been unable to figure out what's wrong so far.

For consistency I have also disabled the generic automatic device
switching feature.

With this change, mini_al will automatically switch the internal device
to that of the new default device when the user changes it via the
operating system's sound preferences.