Fix BMenu behaviour/ABI by reinstating BMenu::InvalidateLayout()

It turns out,this is an old method added by Be, and is not really related to BView::InvalidateLayout(bool). In fact BMenu::InvalidateLayout() does something separate, but related to the BView method. I was wrong to delete this method, since it needs to have action taken each time it is called, so moving these actions into LayoutInvalidated() only worked sometimes (when the BView was considered to have a valid layout).

I have added a comment for future hackers so that they don't delete this method.

headers/os/interface/Menu.h

@@ -78,6 +78,8 @@ public:
 	virtual	void				FrameMoved(BPoint newPosition);
 	virtual	void				FrameResized(float newWidth, float newHeight);
 
+			void				InvalidateLayout();
+
 	virtual void				MakeFocus(bool focus = true);
 
 			bool				AddItem(BMenuItem* item);

src/kits/interface/Menu.cpp

@@ -667,6 +667,17 @@ BMenu::FrameResized(float new_width, float new_height)
 }
 
 
+void
+BMenu::InvalidateLayout()
+{
+	fUseCachedMenuLayout = false;
+	// This method exits for backwards compatibility reasons, it is used to
+	// invalidate the menu layout, but we also use call
+	// BView::InvalidateLayout() for good measure. Don't delete this method!
+	BView::InvalidateLayout(false);
+}
+
+
 // #pragma mark -