GM's CEO Pours Cold Water on Gas Tax Hike  DETROIT (Reuters) - General Motors Corp. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=GM.N target=/stocks/quickinfo/fullquote"&gt;GM.N&lt;/A&gt; on Friday  said Americans had no need to worry about talk of higher  federal gasoline taxes being used to curb their dependency on  foreign oil.