sdl2 :: Mix :: volume_chunk
volume for chunk, out of mix.max_volumeIf volume == -1, only read the previous value.
Returns the previous volume value.
	# Set the `volume` for `chunk`, out of `mix.max_volume`
	#
	# If `volume == -1`, only read the previous value.
	#
	# Returns the previous volume value.
	fun volume_chunk(chunk: MixChunk, volume: Int) `{
		Mix_VolumeChunk(chunk, volume);
	`}
					lib/sdl2/mixer.nit:142,2--149,3