moved wxMenuBar::FindMenu(title) from MSW to common code

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@6202 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/menu.h

@@ -297,6 +297,9 @@ public:
     // if menu is !NULL, it will be filled with wxMenu this item belongs to
     virtual wxMenuItem* FindItem(int id, wxMenu **menu = NULL) const = 0;
 
+    // find menu by its caption, return wxNOT_FOUND on failure
+    int FindMenu(const wxString& title);
+
     // item access
     // -----------