title: No transparency on OpenglES layer on iOS simulator
body: <p>On my IOS application, I have a screen with 2 views : one classic UIView and one openGLES view. 
  The 3d view is over the 2d and I set a clear background to see the 2d view behind it.</p>
  
  <p>it is displayed as expected on all ios devices but the 3d view is opaque on ios simulator.
  On the 3DView I use these lines : </p>
  
  <pre><code>[myOpenGLView setBackgroundColor:[UIColor clearColor]];
  [myOpenGLView setOpaque:NO];
  </code></pre>
  
  <p>And before each render I call :</p>
  
  <pre><code>glClearColor(0.,0.,0.,0.);
  glClear(GL_COLOR_BUFFER_BIT);
  </code></pre>
  
  <p>Does anybody got the same problem ?</p>