Wal-Mart Give Retailers Upbeat '05 Start  NEW YORK (Reuters) - Wal-Mart Stores Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=WMT.N target=/stocks/quickinfo/fullquote"&gt;WMT.N&lt;/A&gt;, the  world's biggest retailer, on Monday said December sales would  be at the top end of its outlook on better-than-expected  post-Christmas spending, sending its shares up 2 percent.