Military Buoys Profit at Defense Firms  CHICAGO (Reuters) - Robust demand for military equipment  and technology led four U.S. defense companies to post higher  quarterly profit on Wednesday, with jet maker Boeing Co. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=BA.N target=/stocks/quickinfo/fullquote"&gt;BA.N&lt;/A&gt;  reporting a 78 percent jump in earnings despite a decline in  commercial airplane revenue.