title: jQuery masked input with datepicker fires onChange event even when not changed
body: <p>I have an input ( id="myDate" ), a datepicher and mask attached to it</p>
  
  <p>When user presses the Tab key to circulate through all the controls, and reaches to the input "myDate", </p>
  
  <pre><code>__/__/____
  </code></pre>
  
  <p>is shown because of :</p>
  
  <pre><code>$("#myDate").mask("99/99/9999");
  </code></pre>
  
  <p>the problem is when user presses Tab to leave the control without writing anything, the onChange event is fired, which is expected only when user modifies the control value !</p>
  
  <p>how to detect real change, and ignore the </p>
  
  <pre><code>__/__/____
  </code></pre>
  
  <p>added and removed by the jQuery mask ?</p>