Cablevision Posts Narrower Loss  NEW YORK (Reuters) - Cablevision Systems Corp. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=CVC.N target=/stocks/quickinfo/fullquote"&gt;CVC.N&lt;/A&gt; on  Tuesday posted a smaller third-quarter net loss as revenue rose  20 percent..