[gui] don't remove lablgtk2 compatibility too early

.gitignore

@@ -201,3 +201,4 @@ hello-*.tar.gz
 /src/plugins/gui/GSourceView2.ml
 /src/plugins/gui/dgraph.ml
 /src/plugins/gui/dgraph.mli
+/src/plugins/gui/gtk_compat.ml

Makefile

@@ -705,7 +705,19 @@ src/plugins/gui/dgraph.mli: src/plugins/gui/dgraph.mli.in
 	$(CHMOD_RO) $@
 endif
 
+ifeq ($(LABLGTK),lablgtk3)
+src/plugins/gui/gtk_compat.ml: src/plugins/gui/gtk_compat.3.ml
+	$(CP) $< $@
+	$(CHMOD_RO) $@
+else
+src/plugins/gui/gtk_compat.ml: src/plugins/gui/gtk_compat.2.ml
+	$(CP) $< $@
+	$(CHMOD_RO) $@
+endif
+GENERATED+=src/plugins/gui/gtk_compat.ml
+
 SINGLE_GUI_CMO:= \
+	gtk_compat \
 	$(WTOOLKIT) \
 	$(SOURCEVIEWCOMPAT) \
 	$(DGRAPHCOMPAT) \

src/plugins/gui/gtk_compat.2.ml

+let get_toolbar_index (toolbar:GButton.toolbar) (item:GButton.tool_item) =
+  toolbar#get_item_index item

src/plugins/gui/gtk_compat.3.ml

+let get_toolbar_index toolbar item = toolbar#get_item_index item#as_tool_item

src/plugins/gui/gtk_compat.mli

+val get_toolbar_index: GButton.toolbar -> GButton.tool_item -> int

src/plugins/gui/menu_manager.ml

@@ -165,7 +165,10 @@ class menu_manager ?packing ~host:(_:Gtk_helper.host) =
            By default, add all the others just before this very first group. *)
         ref (match pos, first_tool_separator with
             | None, None -> 0
-            | None, Some sep -> max 0 (toolbar#get_item_index sep#as_tool_item)
+            | None, Some sep ->
+              max
+                0
+                (Gtk_compat.get_toolbar_index toolbar (sep:>GButton.tool_item))
             | Some p, _ -> p)
       in
       let toolbar_packing w =