* ma_rb_reset()
* ma_rb_available_read()
* ma_rb_available_write()
* ma_pcm_rb_reset()
* ma_pcm_rb_available_read()
* ma_pcm_rb_available_write()

Fix a few tiny memory leaks

This happens when stopping the device while nothing is being played and
is due to how WASAPI does not signal an event in loopback mode when
nothing is being played.