Set the volume for chunk, out of mix.max_volume

If volume == -1, only read the previous value.

Returns the previous volume value.

Property definitions

sdl2 $ Mix :: volume_chunk
	# 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