All objects of the datetime module have macros to access their properties, except timedelta.
This simple patch adds the macros PyDateTime_DELTA_GET_DAYS, PyDateTime_DELTA_GET_SECONDS, PyDateTime_DELTA_GET_MICROSECONDS; module developers are encouraged to use these instead of obj->seconds for example.

Motivation:
PyPy cannot easily expose PyDateTime_Delta fields because datetime is implemented as a pure Python module and it's difficult to rebuild a C structure from a heap type.
In PyPy these macros are actually functions, which do something similar to PyLong_AsLong(PyObject_GetAttrString(obj, "seconds")):
https://bitbucket.org/pypy/pypy/src/b67e65d709e1/pypy/module/cpyext/cdatetime.py#cl-235