[gtk+/center-box: 2/7] export the center box api

[Matthias Clasen <matthiasc src gnome org>]

commit 81049ea5c5b64ecca15367cc67364b2ff4ccb119
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Jun 3 09:08:13 2017 -0400

    export the center box api
    
    Without this, its not a public api after all...

 gtk/gtkcenterbox.h |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkcenterbox.h b/gtk/gtkcenterbox.h
index c18845c..bf13f39 100644
--- a/gtk/gtkcenterbox.h
+++ b/gtk/gtkcenterbox.h
@@ -48,18 +48,26 @@ struct _GtkCenterBoxClass
   GtkWidgetClass parent_class;
 };
 
+GDK_AVAILABLE_IN_3_92
 GType      gtk_center_box_get_type (void) G_GNUC_CONST;
 
+GDK_AVAILABLE_IN_3_92
 GtkWidget *gtk_center_box_new (void);
+GDK_AVAILABLE_IN_3_92
 void       gtk_center_box_set_start_widget   (GtkCenterBox *self,
                                               GtkWidget    *child);
+GDK_AVAILABLE_IN_3_92
 void       gtk_center_box_set_center_widget  (GtkCenterBox *self,
                                               GtkWidget    *child);
+GDK_AVAILABLE_IN_3_92
 void       gtk_center_box_set_end_widget     (GtkCenterBox *self,
                                               GtkWidget    *child);
 
+GDK_AVAILABLE_IN_3_92
 GtkWidget * gtk_center_box_get_start_widget  (GtkCenterBox *self);
+GDK_AVAILABLE_IN_3_92
 GtkWidget * gtk_center_box_get_center_widget (GtkCenterBox *self);
+GDK_AVAILABLE_IN_3_92
 GtkWidget * gtk_center_box_get_end_widget    (GtkCenterBox *self);