Add wxUSE_MENUBAR build option, off by default in wxiOS

Allow building without wxMenuBar (but with wxMenu), as this class
doesn't exist and can't be reasonably implemented under iOS (but
wxMenu can and should be, as it's widely used in iOS 14 UI).

include/wx/frame.h

@@ -23,7 +23,9 @@ extern WXDLLIMPEXP_DATA_CORE(const char) wxStatusLineNameStr[];
 extern WXDLLIMPEXP_DATA_CORE(const char) wxToolBarNameStr[];
 
 class WXDLLIMPEXP_FWD_CORE wxFrame;
+#if wxUSE_MENUBAR
 class WXDLLIMPEXP_FWD_CORE wxMenuBar;
+#endif
 class WXDLLIMPEXP_FWD_CORE wxMenuItem;
 class WXDLLIMPEXP_FWD_CORE wxStatusBar;
 class WXDLLIMPEXP_FWD_CORE wxToolBar;
@@ -78,6 +80,7 @@ public:
     // ------------------
 
 #if wxUSE_MENUS
+#if wxUSE_MENUBAR
     virtual void SetMenuBar(wxMenuBar *menubar);
     virtual wxMenuBar *GetMenuBar() const { return m_frameMenuBar; }
 
@@ -85,7 +88,7 @@ public:
     // and exists mainly in order to be overridden in the MDI parent frame
     // which also looks at its active child menu bar
     virtual wxMenuItem *FindItemInMenuBar(int menuId) const;
-
+#endif
     // generate menu command corresponding to the given menu item
     //
     // returns true if processed
@@ -192,7 +195,7 @@ protected:
     // test whether this window makes part of the frame
     virtual bool IsOneOfBars(const wxWindow *win) const wxOVERRIDE;
 
-#if wxUSE_MENUS
+#if wxUSE_MENUBAR
     // override to update menu bar position when the frame size changes
     virtual void PositionMenuBar() { }
 
@@ -203,13 +206,15 @@ protected:
     // override to do something special when the menu bar is attached to the
     // frame
     virtual void AttachMenuBar(wxMenuBar *menubar);
+#endif // wxUSE_MENUBAR
 
     // Return true if we should update the menu item state from idle event
     // handler or false if we should delay it until the menu is opened.
     static bool ShouldUpdateMenuFromIdle();
 
+#if wxUSE_MENUBAR
     wxMenuBar *m_frameMenuBar;
-#endif // wxUSE_MENUS
+#endif // wxUSE_MENUBAR
 
 #if wxUSE_STATUSBAR && (wxUSE_MENUS || wxUSE_TOOLBAR)
     // the saved status bar text overwritten by DoGiveHelp()