[gtkmm/boolfilter_multisorter] Gtk::MultiSorter: add interfaces

[Andreas Persson <andreasp src gnome org>]

commit 661a6b27ff52885f6cd34cf1019cf8fcfc7f3c4c
Author: Andreas Persson <andreasp56 outlook com>
Date:   Mon Sep 28 19:49:09 2020 +0200

    Gtk::MultiSorter: add interfaces
    
    Gtk::MultiSorter implements the Gio::ListModel and Gtk::Buildable
    interfaces.

 gtk/src/multisorter.hg | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
---
diff --git a/gtk/src/multisorter.hg b/gtk/src/multisorter.hg
index ab7a3142..a4590e5c 100644
--- a/gtk/src/multisorter.hg
+++ b/gtk/src/multisorter.hg
@@ -15,6 +15,8 @@
  */
 
 #include <gtkmm/sorter.h>
+#include <gtkmm/buildable.h>
+#include <giomm/listmodel.h>
 
 _DEFS(gtkmm,gtk)
 _PINCLUDE(gtkmm/private/sorter_p.h)
@@ -30,9 +32,11 @@ namespace Gtk
  *
  * @newin{3,98}
  */
-class GTKMM_API MultiSorter : public Sorter
+class GTKMM_API MultiSorter : public Sorter, public Gio::ListModel, public Buildable
 {
   _CLASS_GOBJECT(MultiSorter, GtkMultiSorter, GTK_MULTI_SORTER, Gtk::Sorter, GtkSorter, , , GTKMM_API)
+  _IMPLEMENTS_INTERFACE(Gio::ListModel)
+  _IMPLEMENTS_INTERFACE(Buildable)
   _STRUCT_NOT_HIDDEN
 
 protected: