Clean up a couple of warnings on Win64. The downcast of the strlen size_t

return value to int is safe here because in each case it previouls checked that
there will be no overflow.

Python/bltinmodule.c

@@ -430,7 +430,7 @@ complex_from_string(PyObject *v)
 					    NULL))
 			return NULL;
 		s = s_buffer;
-		len = strlen(s);
+		len = (int)strlen(s);
 	}
 	else if (PyObject_AsCharBuffer(v, &s, &len)) {
 		PyErr_SetString(PyExc_TypeError,