force provision of "menu-name" for all WindowProxy objects, and thus Tabbables

Actions for hide/show/attach/detach tabbables use hard-coded names which are not
translated. Using Tabbable/WindowProxy::name() to lookup the action will fail,
since the name can be translated. This changes just removes the option to not
provide a menu-name when creating these objects, and uses the name menu-name
when looking up an action by name

libs/gtkmm2ext/gtkmm2ext/window_proxy.h

@@ -40,7 +40,6 @@ class VisibilityTracker;
 class LIBGTKMM2EXT_API WindowProxy : public PBD::StatefulDestructible, public virtual sigc::trackable
 {
 public:
-	WindowProxy (const std::string& name);
 	WindowProxy (const std::string& name, const std::string& menu_name);
 	WindowProxy (const std::string& name, const std::string& menu_name, const XMLNode&);
 	virtual ~WindowProxy();

libs/gtkmm2ext/window_proxy.cc

@@ -31,19 +31,6 @@ using namespace Gtk;
 using namespace Gtkmm2ext;
 using namespace PBD;
 
-WindowProxy::WindowProxy (const std::string& name)
-	: _name (name)
-	, _window (0)
-	, _visible (false)
-	, _x_off (-1)
-	, _y_off (-1)
-	, _width (-1)
-	, _height (-1)
-	, vistracker (0)
-	, _state_mask (StateMask (Position|Size))
-{
-}
-
 WindowProxy::WindowProxy (const std::string& name, const std::string& menu_name)
 	: _name (name)
 	, _menu_name (menu_name)

libs/widgets/tabbable.cc

@@ -37,8 +37,8 @@ using namespace Gtk;
 using namespace Gtkmm2ext;
 using namespace ArdourWidgets;
 
-Tabbable::Tabbable (Widget& w, const string& name, bool tabbed_by_default)
-	: WindowProxy (name)
+Tabbable::Tabbable (Widget& w, const string& visible_name, string const & nontranslatable_name, bool tabbed_by_default)
+	: WindowProxy (visible_name, nontranslatable_name)
 	, _contents (w)
 	, _parent_notebook (0)
 	, tab_requested_by_state (tabbed_by_default)

libs/widgets/widgets/tabbable.h

@@ -44,7 +44,7 @@ namespace ArdourWidgets {
 class LIBWIDGETS_API Tabbable : public Gtkmm2ext::WindowProxy
 {
 public:
-	Tabbable (Gtk::Widget&, const std::string&, bool tabbed_by_default = true);
+	Tabbable (Gtk::Widget&, const std::string& user_visible_name, std::string const & untranslated_name, bool tabbed_by_default = true);
 	~Tabbable ();
 
 	void add_to_notebook (Gtk::Notebook& notebook, const std::string& tab_title);