tests/basics: Add test for subclassing an iterable native type.

tests/basics/subclass_native_iter.py

@@ -0,0 +1,7 @@
+# test subclassing a native type which can be iterated over
+
+class mymap(map):
+    pass
+
+m = mymap(lambda x: x + 10, range(4))
+print(list(m))