C++ compile cleanup: proper declaration of _Py_BuildValue_SizeT

Include/modsupport.h

@@ -29,6 +29,7 @@ PyAPI_FUNC(int) PyArg_ParseTupleAndKeywords(PyObject *, PyObject *,
                                                   const char *, char **, ...);
 PyAPI_FUNC(int) PyArg_UnpackTuple(PyObject *, const char *, Py_ssize_t, Py_ssize_t, ...);
 PyAPI_FUNC(PyObject *) Py_BuildValue(const char *, ...);
+PyAPI_FUNC(PyObject *) _Py_BuildValue_SizeT(const char *, ...);
 PyAPI_FUNC(int) _PyArg_NoKeywords(const char *funcname, PyObject *kw);
 
 PyAPI_FUNC(int) PyArg_VaParse(PyObject *, const char *, va_list);