title: GLKit's -drawRect: is not called during screen rotation
body: <p>I have <code>GLKit</code>-based app with some simple object displayed.</p>
  
  <p>All works fine, except screen rotation, during which <code>GLKView</code> is not updated (<code>-drawRect:</code> is not called). So during rotation projection matrix is not updated according to dynamically changing screen sizes and object looks badly (stretched).</p>