Winn-Dixie Posts Loss But Sees Progress  NEW YORK (Reuters) - Grocer Winn-Dixie Stores Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=WIN.N target=/stocks/quickinfo/fullquote"&gt;WIN.N&lt;/A&gt;  on Thursday reported a quarterly loss as restructuring costs  weighed on results, but said its efforts to reverse a market  share slide are gaining momentum.