[gtk+] centerbox: Add G_BEGIN_DECLS and G_END_DECLS

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 8f22078787c86d3b914e82daa62140b324e8681c
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Sat Aug 5 11:26:42 2017 +0200

    centerbox: Add G_BEGIN_DECLS and G_END_DECLS
    
    https://bugzilla.gnome.org/show_bug.cgi?id=785280

 gtk/gtkcenterbox.h |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkcenterbox.h b/gtk/gtkcenterbox.h
index 460db57..4c8e7ad 100644
--- a/gtk/gtkcenterbox.h
+++ b/gtk/gtkcenterbox.h
@@ -24,6 +24,8 @@
 
 #include "gtkwidget.h"
 
+G_BEGIN_DECLS
+
 #define GTK_TYPE_CENTER_BOX                 (gtk_center_box_get_type ())
 #define GTK_CENTER_BOX(obj)                 (G_TYPE_CHECK_INSTANCE_CAST ((obj), GTK_TYPE_CENTER_BOX, 
GtkCenterBox))
 #define GTK_CENTER_BOX_CLASS(klass)         (G_TYPE_CHECK_CLASS_CAST ((klass), GTK_TYPE_CENTER_BOX, 
GtkCenterBoxClass))
@@ -62,4 +64,6 @@ void                gtk_center_box_set_baseline_position (GtkCenterBox        *s
 GDK_AVAILABLE_IN_3_92
 GtkBaselinePosition gtk_center_box_get_baseline_position (GtkCenterBox        *self);
 
+G_END_DECLS
+
 #endif