The hallowed Greatest Generation is a tent big enough to include even the French, so long as they’re resistance fighters striking back against their Nazi oppressors. But is America ready to include soldiers who are both Frenchmen and Arab Muslims? This is the brief for “Days of Glory,” a massive World War II film about France’s colonial forces — mostly North African Muslims — who fought in the vineyards of Provence and Italy to liberate a motherland that had never given them anything but grief.