[gtk+] Add a few missing include guards

[Matthias Clasen <matthiasc src gnome org>]

commit 95d76d0132c22d9ef2b21c713c3a15d9e3a9e54c
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Oct 1 00:49:59 2014 -0400

    Add a few missing include guards

 gtk/gtkapplicationwindow.h |    4 ++++
 gtk/gtkstack.h             |    4 ++++
 gtk/gtkstackswitcher.h     |    4 ++++
 3 files changed, 12 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkapplicationwindow.h b/gtk/gtkapplicationwindow.h
index f0654b3..234283c 100644
--- a/gtk/gtkapplicationwindow.h
+++ b/gtk/gtkapplicationwindow.h
@@ -20,6 +20,10 @@
 #ifndef __GTK_APPLICATION_WINDOW_H__
 #define __GTK_APPLICATION_WINDOW_H__
 
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gtk/gtk.h> can be included directly."
+#endif
+
 #include <gtk/gtkwindow.h>
 
 G_BEGIN_DECLS
diff --git a/gtk/gtkstack.h b/gtk/gtkstack.h
index 3240ada..1f4e7d7 100644
--- a/gtk/gtkstack.h
+++ b/gtk/gtkstack.h
@@ -22,6 +22,10 @@
 #ifndef __GTK_STACK_H__
 #define __GTK_STACK_H__
 
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gtk/gtk.h> can be included directly."
+#endif
+
 #include <gtk/gtkcontainer.h>
 
 G_BEGIN_DECLS
diff --git a/gtk/gtkstackswitcher.h b/gtk/gtkstackswitcher.h
index 093f85f..61f3158 100644
--- a/gtk/gtkstackswitcher.h
+++ b/gtk/gtkstackswitcher.h
@@ -20,6 +20,10 @@
 #ifndef __GTK_STACK_SWITCHER_H__
 #define __GTK_STACK_SWITCHER_H__
 
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gtk/gtk.h> can be included directly."
+#endif
+
 #include <gtk/gtkbox.h>
 #include <gtk/gtkstack.h>