NEW YORK (Reuters) - U.S. stocks rallied on Thursday after a fast retreat in the oil price helped boost confidence among investors, while retailers, such as Best Buy Co. Inc. (BBY.N: Quote, Profile, Research) and Gap Inc (GPS.N: Quote, Profile, Research) , lent support. The stock market was cheered as several retailers beat sales expectations or raised forecasts, pushing up the Standard & Poor's retailing index 2.4 percent. An easing in the oil price also helped sentiment. Crude for October delivery ended up just 5 cents at $44.05 a barrel after gains of more than a dollar earlier pushed it...