title: ios swift CMutableVoidPointer not recognized in observeValueForKeyPath
body: <p>I'm trying to make use of the NSObject(NSKeyValueObserving) in my Swift class but I'm running into a type problem. Xcode is complaining that it doesn't understand the CMutableVoidPointer type for the 'context' argument in the following code:</p>
  
  <pre><code>override func observeValueForKeyPath(keyPath: String!, ofObject object: AnyObject!, change: NSDictionary!, context: CMutableVoidPointer)
  </code></pre>
  
  <p>I use CMutableVoidPointer because the Objective-C definition types the 'context' argument as a void *.</p>
  
  <p>The exact error I'm getting at compile-time is: "Use of undeclared type 'CMutableVoidPointer'".</p>
  
  <p>I'm using Xcode Beta 3.</p>
  
  <p>Any help would be appreciated.</p>