py: Implement fallback for equality check for all types.

Return "not equal" for objects that don't implement equality check.
This is as per Python specs.

tests/basics/equal_class.py

@@ -0,0 +1,25 @@
+# test equality for classes/instances to other types
+
+class A:
+    pass
+
+class B:
+    pass
+
+class C(A):
+    pass
+
+print(A == None)
+print(None == A)
+
+print(A == A)
+print(A() == A)
+print(A() == A())
+
+print(A == B)
+print(A() == B)
+print(A() == B())
+
+print(A == C)
+print(A() == C)
+print(A() == C())