Implemented TME_QUERY and TME_HOVER flags in _TrackMouseEvent and
TrackMouseEventProc.  Added code to allow addition/cancelation of
tracking flags on existing entries rather than create extra entries.
Fixed timer.  Added check to _TrackMouseEvent to stop timer if the
tracking list is empty.  Fixed TME_CANCEL.  Fixed TME_LEAVE/TME_HOVER
when hwndTrack isn't the current hwnd.