Don't generate wxEVT_MENU_{OPEN,CLOSE} for disabled top menus in wxMSW.

Windows still sends these messages even if a top level menu is disabled, for
some reason, so filter them out manually.

Closes #2168.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@78247 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/menu.h

@@ -235,6 +235,9 @@ public:
     void Refresh( bool eraseBackground,
                           const wxRect *rect = (const wxRect *) NULL ) { wxWindow::Refresh(eraseBackground, rect); }
 
+    // Get a top level menu position or wxNOT_FOUND from its handle.
+    int MSWGetTopMenuPos(WXHMENU hMenu) const;
+
     // Get a top level or sub menu with given handle (recursively).
     wxMenu* MSWGetMenu(WXHMENU hMenu) const;