New Device APIs:
  * ma_device_set_master_volume()
  * ma_device_get_master_volume()
  * ma_device_set_master_gain_db()
  * ma_device_get_master_gain_db()

New Helper APIs
  * ma_copy_and_apply_volume_factor_u8()
  * ma_copy_and_apply_volume_factor_s16()
  * ma_copy_and_apply_volume_factor_s24()
  * ma_copy_and_apply_volume_factor_s32()
  * ma_copy_and_apply_volume_factor_f32()
  * ma_apply_volume_factor_u8()
  * ma_apply_volume_factor_s16()
  * ma_apply_volume_factor_s24()
  * ma_apply_volume_factor_s32()
  * ma_apply_volume_factor_f32()
  * ma_copy_and_apply_volume_factor_pcm_frames_u8()
  * ma_copy_and_apply_volume_factor_pcm_frames_s16()
  * ma_copy_and_apply_volume_factor_pcm_frames_s24()
  * ma_copy_and_apply_volume_factor_pcm_frames_s32()
  * ma_copy_and_apply_volume_factor_pcm_frames_f32()
  * ma_copy_and_apply_volume_factor_pcm_frames()
  * ma_apply_volume_factor_pcm_frames_u8()
  * ma_apply_volume_factor_pcm_frames_s16()
  * ma_apply_volume_factor_pcm_frames_s24()
  * ma_apply_volume_factor_pcm_frames_s32()
  * ma_apply_volume_factor_pcm_frames_f32()
  * ma_apply_volume_factor_pcm_frames()
  * ma_factor_to_gain_db()
  * ma_gain_db_to_factor()

This only applies when the playback sample format is configured as
ma_format_f32. Clipping is enabled by default and can be disabled by
setting ma_device_config.noClip to true.

This commit makes it well defined as to whether or not the output
buffer passed in to the data callback is initialized to zero or left
undefined. By default it's initialized to zero, but can be changed to
undefined by setting noPreZeroedOutputBuffer in the device config.

* 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.