Stocks Seen Lower; Inflation Data on Tap  NEW YORK (Reuters) - U.S. stock futures pointed to a  slightly lower market open on Tuesday, as Wall Street awaits  inflation data, while shares of 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;  will be watched after the company posted a higher quarterly  profit.