title: MPVolumeView's slider setVolumeThumbImage:forState: not working on iOS5
body: <p>oI use a MPVolumeView to display a volume slider. I've customized it with </p>
  
  <pre><code>        [myVolumeView setVolumeThumbImage:[UIImage imageNamed:@"sound_slider_knob.png"] forState:UIControlStateNormal];
          [myVolumeView setVolumeThumbImage:[UIImage imageNamed:@"sound_slider_knob.png"] forState:UIControlStateHighlighted];
          [myVolumeView setMaximumVolumeSliderImage:[UIImage imageNamed:@"slider_player_bg.png"] forState:UIControlStateNormal];
          [myVolumeView setMinimumVolumeSliderImage:[UIImage imageNamed:@"slider_player_fg.png"] forState:UIControlStateNormal];
  </code></pre>
  
  <p>everything works fine on iOS6, but on iOS5, I get this error message :</p>
  
  <pre><code>-[MPVolumeView setVolumeThumbImage:forState:]: unrecognized selector sent to instance 0x8c29f30
  -[UIDevice identifierForVendor]: unrecognized selector sent to instance 0x8909b30
  </code></pre>
  
  <p>And it's actually true that in MPVolumeView.h there is </p>
  
  <pre><code>- (void)setVolumeThumbImage:(UIImage *)image forState:(UIControlState)state NS_AVAILABLE_IOS(6_0);
  </code></pre>
  
  <p>Is there any way to custom MPVolumeView in iOS 5 ?</p>