Bad checksum on 'cdata' types

[fsitedev]

require('digest').crc32(10863919174838990);

• 1660621899

require('digest').crc32(10863919174838991);

• 1660621899

[rtsisyk]

 update = function(self, str)
        str = tostring(str or '')
        self.value = ffi.C.crc32_calc(self.value, str, string.len(str))
    end,

tostring(str or '') is a BUG. "any object" to "bytearray" is a separate feature. Don't rely to tostring() for that. tostring() call should be removed. Since this change is not backward-compatible, I added 1.7.0 tag.