title: Handle alt key(s) in UWP application
body: <p>I'm using KeyDown and KeyUp handlers on <code>Window.Current.CoreWindow</code> to catch keystrokes in a VNC application for UWP.  This works great with one exception: alt (<code>VirtualKey.Menu/LeftMenu/RightMenu</code>) never is sent to my application.  In addition, alt+letter results in neither being sent to the handlers.</p>
  
  <p>I assume that this is because some accelerator handler is eating these events before they reach CoreWindow.  Is there any way around this?</p>