Is self a UTF-16 low surrogate ?

Property definitions

core :: abstract_text $ Char :: is_lo_surrogate
	# Is `self` a UTF-16 low surrogate ?
	fun is_lo_surrogate: Bool do
		var cp = code_point
		return cp >= 0xDC00 and cp <= 0xDFFF
	end
lib/core/text/abstract_text.nit:2174,2--2178,4