title: Convert a Unicode string to hexadecimal
body: <p>I want to convert a Unicode string to hexadecimal.</p>
  
  <p>In other words I need to convert a string like <code>أحمد</code> to:</p>
  
  <pre><code>0xC3CDE3CF0000000000000000000000000000000000000000000000000000
  </code></pre>