title: iOS Simulator GL_OES_standard_derivatives
body: <p>On iOS4 GL_OES_standard_derivatives is only supported on the device (from what I see when I output the extensions), is there a way to be able to:</p>
  
  <ol>
  <li><p>Detect in the fragment shader if the extension is supported or not</p></li>
  <li><p>If not supported, does anyone have a the code for the dFdx and dFdy? Can't seems that find anything on google.</p></li>
  </ol>
  
  <p>TIA!</p>