Write a floating point value on 64 bits

Property definitions

binary :: binary $ Writer :: write_double
	# Write a floating point `value` on 64 bits
	fun write_double(value: Float)
	do
		for i in [0..8[ do write_byte value.double_byte_at(i, big_endian)
	end
lib/binary/binary.nit:123,2--127,4