traceback if Python is optimized.
* delay the lookup of the size_t type, it is not available at startup
* The second argument of the PyFrameObjectPtr constructor is optional, as
done in other constructors
* iter_builtins() and iter_globals() methods of PyFrameObjectPtr returns
an empty tuple instead of None if Python is optimized
* Fix py-bt to handle correctly "optimized" frames
* Frame.get_pyop() tries to get the frame pointer from PyEval_EvalCodeEx()
if the pointer is optimized out in PyEval_EvalFrameEx()
Forward port some code from Python3:
* join surrogate pairs if sizeof(Py_UNICODE)==2
* Enable non-BMP test on narrow builds using u"\U0001D121" instead of
unichr(0x1D121)