T-W, Comcast in Pact on Cable Unit Stake  NEW YORK (Reuters) - Time Warner Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=TWX.N target=/stocks/quickinfo/fullquote"&gt;TWX.N&lt;/A&gt; and Comcast  Corp. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=CMCSA.OQ target=/stocks/quickinfo/fullquote"&gt;CMCSA.OQ&lt;/A&gt; on Monday agreed to a pact giving Comcast an  option to cut its stake in Time Warner's cable unit, opening  the door for Comcast to unwind the entire partnership.