Halliburton May Separate KBR Unit  NEW YORK (Reuters) - Halliburton Co. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=HAL.N target=/stocks/quickinfo/fullquote"&gt;HAL.N&lt;/A&gt;, beset by  controversy over its work in Iraq, plans to shed its KBR  engineering and construction unit if the oilfield services  company's share performance does not match its peers, it said  on Thursday.