This swaps the order of the input and output pointers so that it's
consistent with the order used by memcpy().

This removes the two separate callbacks for sending and receiving data
to/from the device to a unified callback that's used for both input and
output. The new callback takes a pointer to both an input and output
buffer. When the device is opened in playback mode the input pointer
will be set to null. Likewise the output pointer will be set to null
for capture devices. Both input and output pointers will be non-null
for full-duplex devices.

This change makes a device run it's own loop with a timer to better
simulate an actual device.

Automatic device switching has not yet been tested with this.

This work is isolated to WASAPI for now while I figure out requirements
and the API.

This will be the basis for an improved main loop in the audio thread.

# Conflicts:
#	mini_al.h

This change makes it consistent with mal_pcm_converter, mal_src, etc.

All functions have been renamed from mal_dsp_*() to
mal_pcm_converter_*(). All structures have been renamed from mal_dsp*
to mal_pcm_converter*.

* Return MAL_SHARE_MODE_NOT_SUPPORTED if SetCooperativeLevel fails.
* Always fail with MAL_SHARE_MODE_NOT_SUPPORTED if exclusive mode is
  requested for capture.