Core and builtins
-----------------
+- code_new (a.k.a new.code()) now checks its arguments sufficiently
+ carefully that passing them on to PyCode_New() won't trigger calls
+ to Py_FatalError() or PyErr_BadInternalCall(). It is still the case
+ that the returned code object might be entirely insane.
+
- Subclasses of string can no longer be interned. The semantics of
interning were not clear here -- a subclass could be mutable, for
example -- and had bugs. Explicitly interning a subclass of string