Apply scaling on x, y, z to this matrix

Property definitions

matrix :: projection $ Matrix :: scale
	# Apply scaling on `x, y, z` to this matrix
	fun scale(x, y, z: Float)
	do
		for i in [0..3] do
			self[0, i] = self[0, i] * x
			self[1, i] = self[1, i] * y
			self[2, i] = self[2, i] * z
		end
	end
lib/matrix/projection.nit:105,2--113,4