[gtkmm] Docs: Fix PlacesSidebar doc generation

[Murray Cumming <murrayc src gnome org>]

commit 35cc79c3839f7e272c20524a85a2bae638a1800c
Author: Murray Cumming <murrayc murrayc com>
Date:   Fri Oct 11 11:57:02 2013 +0200

    Docs: Fix PlacesSidebar doc generation

 gtk/src/gtk_extra_objects.defs |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)
---
diff --git a/gtk/src/gtk_extra_objects.defs b/gtk/src/gtk_extra_objects.defs
index 8a1eeb1..9280917 100644
--- a/gtk/src/gtk_extra_objects.defs
+++ b/gtk/src/gtk_extra_objects.defs
@@ -78,6 +78,13 @@
   (gtype-id "GTK_TYPE_PAGE_SETUP")
 )
 
+; For some reason, the docs generator needs this extra hint:
+(define-object PlacesSidebar
+  (in-module "Gtk")
+  (c-name "GtkPlacesSidebar")
+  (gtype-id "GTK_TYPE_PLACES_SIDEBAR")
+)
+
 (define-object PrintContext
   (in-module "Gtk")
   (c-name "GtkPrintContext")