Compares the two glib.Bytes values.
This function can be used to sort GBytes instances in lexicographical order.
If bytes1 and bytes2 have different length but the shorter one is a prefix of the longer one then the shorter one is considered to be less than the longer one. Otherwise the first byte where both differ is used for comparison. If bytes1 has a smaller value at that position it is considered less, otherwise greater than bytes2.