Deprecate GtkCallbackMarshal and GtkFunction

As they're only used by already deprecated API

https://bugzilla.gnome.org/show_bug.cgi?id=629955

docs/reference/gtk/tmpl/gtktypeutils.sgml

@@ -179,6 +179,7 @@ Defines a function pointer.
 
 @data: #gpointer
 @Returns: #gint
+@Deprecated: 2.24: Use GSourceFunc() instead.
 
 
 <!-- ##### USER_FUNCTION GtkDestroyNotify ##### -->
@@ -198,6 +199,7 @@ Defines a function pointer.
 @data: #gpointer
 @n_args: #guint
 @args: #GtkArg*
+@Deprecated: 2.24:
 
 
 <!-- ##### TYPEDEF GtkSignalMarshaller ##### -->

gtk/gtktypeutils.h

@@ -47,11 +47,13 @@ GType gtk_identifier_get_type (void) G_GNUC_CONST;
  */
 typedef struct _GtkArg	       	     GtkArg;
 typedef struct _GtkObject   	     GtkObject; /* object forward declaration */
+#if !defined (GTK_DISABLE_DEPRECATED) || defined (GTK_COMPILATION)
 typedef gboolean (*GtkFunction)	    (gpointer      data);
 typedef void (*GtkCallbackMarshal)  (GtkObject    *object,
 				     gpointer      data,
 				     guint         n_args,
 				     GtkArg       *args);
+#endif
 
 /* This used to be defined in gtkitemfactory.h, but moved over here after
  * the complete deprecation of that header