Add basic super() test.

tests/basics/class-super.py

@@ -0,0 +1,13 @@
+class Base:
+
+    def meth(self):
+        print("in Base meth")
+
+class Sub(Base):
+
+    def meth(self):
+        print("in Sub meth")
+        return super().meth()
+
+a = Sub()
+a.meth()