[gtk+] Add single-include guard

[Michael Natterer <mitch src gnome org>]

commit becb5057fc26e721e49d16b2cd1edc4834d65ce3
Author: Michael Natterer <mitch gimp org>
Date:   Thu Jul 9 16:30:52 2009 +0200

    Add single-include guard

 gtk/gtkinfobar.h |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkinfobar.h b/gtk/gtkinfobar.h
index cbc206a..530ebfb 100644
--- a/gtk/gtkinfobar.h
+++ b/gtk/gtkinfobar.h
@@ -28,6 +28,10 @@
  * Modified by the GTK+ Team, 2008-2009.
  */
 
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gtk/gtk.h> can be included directly."
+#endif
+
 #ifndef __GTK_INFO_BAR_H__
 #define __GTK_INFO_BAR_H__