Post WM_MOUSELEAVE after WM_MOUSEMOVE when cleaning up the notificati…

…on area

This may be a fix for #350 and #426. If not enough, another solution could be to
disable the tooltip for a limited amount of time (attach to PreviewTrayToolTipOpen,
check for the last cleanup time in the delegate, set e.Handled if too early).

src/wincompose/interop/WinTypes.cs

@@ -43,6 +43,7 @@ internal enum WM : int
     SYSKEYDOWN = 0x104,
     SYSKEYUP   = 0x105,
     MOUSEMOVE  = 0x200,
+    MOUSELEAVE = 0x2A3,
 };
 
 public enum VK : int

src/wincompose/ui/NotificationIcon.xaml.cs

@@ -187,6 +187,7 @@ private void CleanupNotificationArea()
                 for (int y = rect.Top + 4; y < rect.Bottom; y += 8)
                     for (int x = rect.Left + 4; x < rect.Right; x += 8)
                         NativeMethods.PostMessage(area, (uint)WM.MOUSEMOVE, 0, (y << 16) | x);
+                NativeMethods.PostMessage(area, (uint)WM.MOUSELEAVE, 0, 0);
             }
         }