Ambient color, always visible

The RGB values should be premultiplied by the alpha value.

Property definitions

gamnit $ SmoothMaterial :: ambient_color
	# Ambient color, always visible
	#
	# The RGB values should be premultiplied by the alpha value.
	var ambient_color: Array[Float] is writable
lib/gamnit/depth/more_materials.nit:35,2--38,44