title: UIButton title text is not updated even if I update it in Main thread
body: <p>I'm trying to change the title of an <code>UIButton</code> I've created programmatically, when the user clicks in it. So, this is my code to create the <code>UIButton</code>:</p>
  
  <pre><code>myButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, parentView.frame.size.width, parentView.frame.size.height)];
  [myButton setBackgroundColor:[UIColor blackColor]];
  [myButton setAlpha:0.7];
  [myButton setTitle:@"Hello" forState:UIControlStateNormal];
  [myButton addTarget:self action:@selector(userClicked:) forControlEvents:UIControlEventTouchUpInside];
  
  [parentView addSubview:myButton];
  </code></pre>
  
  <p>And, in my <code>userClicked:</code> method, I do:</p>
  
  <pre><code>-(void) userClicked:(UIButton*)button
  {
      NSLog(@"USER CLICKED!!!");
      if ([NSThread isMainThread])
      {
          NSLog(@"is main thread");
      }
  
      [button setTitle:@"Bye" forState:UIControlStateHighlighted];
      [button setTitle:@"Bye" forState:UIControlStateNormal];
      [button setTitle:@"Bye" forState:UIControlStateSelected];
  
      [self someLengthyComputation];
  }
  </code></pre>
  
  <p>The weird thing is that I can see the log messages printed:</p>
  
  <pre><code>USER CLICKED!!! 
  isMainThread
  </code></pre>
  
  <p>But, the title of the button does not change! What am I doing wrong?</p>
  
  <p>EDIT: Setting the title for several states doesn't work either.</p>
  
  <p>EDIT2: If I print the description of button in the debugger window of Xcode, it shows the  right title!</p>
  
  <pre><code>Printing description of button-&gt;_titleView:
  &lt;UIButtonLabel: 0xa4c9310; frame = (95 216; 130 22); text = 'Bye'; clipsToBounds = YES; opaque = NO; userInteractionEnabled = NO; layer = &lt;CALayer: 0xa44f080&gt;&gt;
  </code></pre>