[gtkmm] Adapt dynamic casts for RefPtr as std::shared_ptr.

[Murray Cumming <murrayc src gnome org>]

commit db69b3a57d418ae61d10235f22577417657cad87
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Apr 7 13:36:52 2017 +0200

    Adapt dynamic casts for RefPtr as std::shared_ptr.

 gtk/src/flowbox.hg |    2 +-
 gtk/src/listbox.hg |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gtk/src/flowbox.hg b/gtk/src/flowbox.hg
index 2331f09..7048357 100644
--- a/gtk/src/flowbox.hg
+++ b/gtk/src/flowbox.hg
@@ -336,7 +336,7 @@ GtkWidget* FlowBox::proxy_bind_list_store_create_widget_callback(void* item, voi
     // class MyObject : public Glib::Object
     // take_copy is true here, because wrap() returns a Glib::RefPtr<>.
     // cobject will be unreferenced when the RefPtr is deleted.
-    Gtk::Widget* widget = slot(Glib::RefPtr<T_item>::cast_dynamic(Glib::wrap(cobject, true)));
+    Gtk::Widget* widget = slot(std::dynamic_pointer_cast<T_item>(Glib::wrap(cobject, true)));
     if (widget)
       return widget->gobj();
   }
diff --git a/gtk/src/listbox.hg b/gtk/src/listbox.hg
index 55cfddd..3b0471f 100644
--- a/gtk/src/listbox.hg
+++ b/gtk/src/listbox.hg
@@ -366,7 +366,7 @@ GtkWidget* ListBox::proxy_bind_list_store_create_widget_callback(void* item, voi
     // class MyObject : public Glib::Object
     // take_copy is true here, because wrap() returns a Glib::RefPtr<>.
     // cobject will be unreferenced when the RefPtr is deleted.
-    Gtk::Widget* widget = slot(Glib::RefPtr<T_item>::cast_dynamic(Glib::wrap(cobject, true)));
+    Gtk::Widget* widget = slot(std::dynamic_pointer_cast<T_item>(Glib::wrap(cobject, true)));
     if (widget)
       return widget->gobj();
   }