title: Swift int constructor to convert hex string
body: <p>All these calls return <code>nil</code> for me:</p>
  
  <pre><code>Int("ff000000", radix: 16)
  Int("#ff000000", radix: 16)
  Int("0xff000000", radix: 16)
  </code></pre>
  
  <p>I must be doing something wrong.</p>