* Add hot key handled return indicator to DRAW_FRAME::GeneralControl() and
  DRAW_FRAME::OnHotKey() and all classed derived from DRAW_FRAME.
* Add code to all GeneralControl() and OnHotKey() functions to return true if
  hot key was handled.
* Call event skip in DRAW_PANEL::OnKeyEvent() when key event is not handled to
  allow default menu event handler to function properly.