xortool-xor is not python 3 compatible

```
Traceback (most recent call last):
  File "/python/bin/xortool-xor", line 117, in <module>
    main()
  File "/python/bin/xortool-xor", line 51, in main
    sys.stdout.write(xor(datas, nocycle=nocycle))
  File "/python/bin/xortool-xor", line 66, in xor
    for i in xrange(maxlen):
NameError: name 'xrange' is not defined
```

`xrange` was replaced by `range` in Python 3