SF bug 684667: Modules/selectmodule.c returns NULL without exception set.

select_select() didn't set an exception in the SELECT_USES_HEAP case when
malloc() returned NULL.

Modules/selectmodule.c

@@ -248,7 +248,7 @@ select_select(PyObject *self, PyObject *args)
 		if (rfd2obj) PyMem_DEL(rfd2obj);
 		if (wfd2obj) PyMem_DEL(wfd2obj);
 		if (efd2obj) PyMem_DEL(efd2obj);
-		return NULL;
+		return PyErr_NoMemory();
 	}
 #endif /* SELECT_USES_HEAP */
 	/* Convert lists to fd_sets, and get maximum fd number