Move single-include guards inside include guards

gcc has optimizations for include guards that only work
if they are outermost in the the header.
https://bugzilla.gnome.org/show_bug.cgi?id=689810

gtk/gtkaspectframe.h

@@ -22,14 +22,14 @@
  * GTK+ at ftp://ftp.gtk.org/pub/gtk/.
  */
 
-#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
-#error "Only <gtk/gtk.h> can be included directly."
-#endif
-
 #ifndef __GTK_ASPECT_FRAME_H__
 #define __GTK_ASPECT_FRAME_H__
 
 
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gtk/gtk.h> can be included directly."
+#endif
+
 #include <gtk/gtkframe.h>