tests/int_big_xor: Test that xor result is normalized.

And thus can be successfully used in comparisons, etc.

tests/basics/int_big_xor.py

@@ -5,3 +5,4 @@ print((1 << 80) ^ 0)
 a = 0xfffffffffffffffffffffffffffff
 print(a ^ (1 << 100))
 print(a ^ (1 << 200))
+print(a ^ a == 0)