Should shadow be drawn? Would use depth_texture and light_mvp.

Property definitions

gamnit $ BlinnPhongProgram :: use_shadows
	# Should shadow be drawn? Would use `depth_texture` and `light_mvp`.
	var use_shadows = uniforms["use_shadows"].as(UniformBool) is lazy
lib/gamnit/depth/more_materials.nit:587,2--588,66