title: Rotate UIBarButtonItem
body: <p>I want to rotate a <code>UIBarButtonItem</code>.</p>
  
  <p>I have been able to do this with <code>UIButton</code>s using <code>setTransform:CGAffineTransformMakeRotation(…)</code>, but <code>UIBarButtonItem</code> does not have this property.</p>
  
  <p>I know the Camera-app does this, so it should be achieveable.<br>
  How can I achieve this?</p>
  
  <p>Thanks.</p>