McDonald's Same-Store Sales Rose 3.9 Pct  CHICAGO (Reuters) - McDonald's Corp. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=MCD.N target=/stocks/quickinfo/fullquote"&gt;MCD.N&lt;/A&gt; on Wednesday  said worldwide sales at its namesake restaurants open more than  a year rose 3.9 percent in August, helped by strong sales of  new menu items like fried chicken strips.