Minor edit to presentation role spec

The second bullet use case example for the presentation role [1] 
mentions a "Labelledby" attribute:

    * An image that is in a container having the same role and where the
      full equivalent is available in text that is marked up with
      Labelledby and (if needed) |aria-describedby|
      <http://www.w3.org/TR/wai-aria/#aria-describedby>;


That should be "aria-labelledby":

    * An image that is in a container having the same role and where the
      full equivalent is available in text that is marked up with
      |aria-labelledby|
      <http://www.w3.org/TR/wai-aria/##aria-labelledby> and (if needed)
      |aria-describedby| <http://www.w3.org/TR/wai-aria/#aria-describedby>;



[1] http://www.w3.org/TR/wai-aria/#presentation

-- 
Joseph Scheuhammer, Ph.D.
Accessibilty Software Architect
Adaptive Technology Research Centre
University of Toronto

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Fax: 416-971-2629

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