tests: Add basic tests for subclassing native types and using special methods.

Even of these, some features do not yet work as expected.

tests/basics/subclass-native1.py

+class mylist(list):
+    pass
+
+a = mylist([1, 2, 5])
+# Test setting instance attr
+a.attr = "something"
+# Test base type __str__
+print(a)
+# Test getting instance attr
+print(a.attr)
+# Test base type ->subscr
+print(a[-1])
+a[0] = -1
+print(a)
+# Test another base type unary op
+print(len(a))
+
+# Test binary op of base type, with 2nd arg being raw base type
+print(a + [20, 30, 40])
+# Test binary op of base type, with 2nd arg being same class as 1st arg
+# TODO: Faults
+#print(a + a)
+
+def foo():
+    print("hello from foo")
+
+try:
+    class myfunc(type(foo)):
+        pass
+except TypeError:
+    print("TypeError")

tests/basics/subclass-native2.py

+class Base1:
+    def __init__(self, *args):
+        print("Base1.__init__",args)
+
+class Clist1(Base1, list):
+    pass
+
+class Ctuple1(Base1, tuple):
+    pass
+
+a = Clist1()
+print(len(a))
+a = Clist1([1, 2, 3])
+print(len(a))
+
+a = Ctuple1()
+print(len(a))
+a = Ctuple1([1, 2, 3])
+# TODO: Faults
+#print(len(a))
+
+print("---")
+
+class Clist2(list, Base1):
+    pass
+
+class Ctuple2(tuple, Base1):
+    pass
+a = Clist2()
+print(len(a))
+a = Clist2([1, 2, 3])
+print(len(a))
+
+#a = Ctuple2()
+#print(len(a))
+#a = Ctuple2([1, 2, 3])
+#print(len(a))