- The interp->builtins variable (and hence, __main__.__builtins__) is
once again initialized to the built-in *module* instead of its
dictionary.

- The finalization order is once again changed.  Signals are finalized
relatively early, because (1) it DECREF's the signal handlers, and if
a signal handler happens to be a bound method, deleting it could cause
problems when there's no current thread around, and (2) we don't want
to risk executing signal handlers during finalization.