Gap Third-Quarter Earnings Tick Up 1 Pct  NEW YORK (Reuters) - Clothing retailer Gap Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=GPS.N target=/stocks/quickinfo/fullquote"&gt;GPS.N&lt;/A&gt;  said on Thursday its quarterly earnings ticked up 1 percent,  buoyed by improved profit margins, but hemmed in by weakness at  its Old Navy and international Gap stores.