Stocks Flat; AIG Offsets Oil Stocks  NEW YORK (Reuters) - Stocks were little changed on Monday  as gains in insurance company American International Group Inc.  &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=AIG.N target=/stocks/quickinfo/fullquote"&gt;AIG.N&lt;/A&gt; and software maker Microsoft Corp. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=MSFT.O target=/stocks/quickinfo/fullquote"&gt;MSFT.O&lt;/A&gt; offset  losses in energy stocks due to lower oil prices.