Jabil Posts Profit on Stronger Demand  SAN FRANCISCO (Reuters) - Contract electronics manufacturer  Jabil Circuit Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=JBL.N target=/stocks/quickinfo/fullquote"&gt;JBL.N&lt;/A&gt; on Tuesday posted a quarterly profit  that more than doubled on stronger demand for computers,  cellphones and other electronic products.