Stocks End Flat, Microsoft Lifts Techs  NEW YORK (Reuters) - U.S. stocks closed little changed on  Monday as investors paused for breath following significant  gains in the market so far this month, while lower oil prices  weighed on energy shares, including Exxon Mobil Corp. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=XOM.N target=/stocks/quickinfo/fullquote"&gt;XOM.N&lt;/A&gt;.