title: WinRT HttpClient header Authorization with multiple values
body: <p>I need to set the Authorization header for Amazon SQS but it requires multiple values.</p>
  
  <p>When setting the header I get an exception thrown:</p>
  
  <blockquote>
    <p>System.FormatException : Cannot add value because header 'Authorization' does not support multiple values.</p>
  </blockquote>
  
  <p>How can I set the header with multiple values separated by a comma. </p>