title: Arithmetic on two CGPoints with + or - operators
body: <p>In Objective-C I'm starting to work with <code>CGPoints</code> and when I need to add two of them the way I'm doing it is this:</p>
  
  <pre><code>CGPoint p1 = CGPointMake(3, 3);
  CGPoint p2 = CGPointMake(8, 8);
  CGPoint p3 = CGPointMake(p2.x-p1.x, p2.y-p1.y);
  </code></pre>
  
  <p>I would like to be able to just do:</p>
  
  <pre><code>CGPoint p3 = p2 - p1;
  </code></pre>
  
  <p>Is that possible?</p>