Sears Shares Soar as Vornado Boosts Stake  NEW YORK (Reuters) - Sears, Roebuck   Co. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=S.N target=/stocks/quickinfo/fullquote"&gt;S.N&lt;/A&gt; shares  jumped as much as 25 percent on Friday after real estate  company Vornado Realty Trust &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=VNO.N target=/stocks/quickinfo/fullquote"&gt;VNO.N&lt;/A&gt; said it raised its stake  in the retailer, a step that could lead Sears convert some of  its real estate assets into cash.