Rewrite insertion of menu items by null and Nyquist modules...

... using the new registration system, and without the fragile hacks making
assumptions about the positions of menus within the menu bar.

src/Menus.cpp

@@ -32,7 +32,6 @@
 
 #include <wx/frame.h>
 
-#include "ModuleManager.h"
 #include "Project.h"
 #include "ProjectHistory.h"
 #include "ProjectSettings.h"
@@ -1046,8 +1045,6 @@ void MenuCreator::RebuildMenuBar(AudacityProject &project)
    CommandManager::Get( project ).PurgeData();
 
    CreateMenusAndCommands(project);
-
-   ModuleManager::Get().Dispatch(MenusRebuilt);
 }
 
 void MenuManager::OnUndoRedo( wxCommandEvent &evt )

src/ModuleManager.h

@@ -38,8 +38,7 @@ typedef enum
    AppInitialized,
    AppQuiting,
    ProjectInitialized,
-   ProjectClosing,
-   MenusRebuilt
+   ProjectClosing
 } ModuleDispatchTypes;
 
 typedef int (*fnModuleDispatch)(ModuleDispatchTypes type);

src/commands/CommandManager.cpp

@@ -477,26 +477,6 @@ wxMenu * CommandManager::CurrentMenu() const
    return tmpCurrentSubMenu;
 }
 
-void CommandManager::SetCurrentMenu(wxMenu * menu)
-{
-   // uCurrentMenu ought to be null in correct usage
-   wxASSERT(!uCurrentMenu);
-   // Make sure of it anyway
-   uCurrentMenu.reset();
-
-   mCurrentMenu = menu;
-}
-
-void CommandManager::ClearCurrentMenu()
-{
-   // uCurrentMenu ought to be null in correct usage
-   wxASSERT(!uCurrentMenu);
-   // Make sure of it anyway
-   uCurrentMenu.reset();
-
-   mCurrentMenu = nullptr;
-}
-
 
 
 void CommandManager::AddItem(AudacityProject &project,

src/commands/CommandManager.h

@@ -133,8 +133,6 @@ class AUDACITY_DLL_API CommandManager final
 
    std::unique_ptr<wxMenuBar> AddMenuBar(const wxString & sMenu);
 
-   // You may either called SetCurrentMenu later followed by ClearCurrentMenu,
-   // or else BeginMenu followed by EndMenu.  Don't mix them.
    wxMenu *BeginMenu(const TranslatableString & tName);
    void EndMenu();
 
@@ -235,11 +233,6 @@ class AUDACITY_DLL_API CommandManager final
    void Check(const CommandID &name, bool checked);
    void Modify(const wxString &name, const TranslatableString &newLabel);
 
-   // You may either called SetCurrentMenu later followed by ClearCurrentMenu,
-   // or else BeginMenu followed by EndMenu.  Don't mix them.
-   void SetCurrentMenu(wxMenu * menu);
-   void ClearCurrentMenu();
-
    //
    // Modifying accelerators
    //