title: Convert UnsafeMutableRawPointer to UnsafeMutablePointer<T> in swift 3
body: <p>I have this code</p>
  
  <pre><code>let grayData = UnsafeMutablePointer&lt;UInt8&gt;(other: malloc(width * height * sizeof(UInt8)))
  </code></pre>
  
  <p>Which doesn't compile in Swift 3. How do I fix this?</p>