Black to Quit Hollinger Inc., Stock Soars  TORONTO (Reuters) - Former press baron Conrad Black will  quit as chairman and chief executive of his Canadian holding  company, Hollinger Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=HLGc.TO target=/stocks/quickinfo/fullquote"&gt;HLGc.TO&lt;/A&gt;, to facilitate his offer to  take it private.