[gtk+] Make GTK_TREE_SORTABLE_*_SORT_COLUMN_ID defines instead of enum

[William Jon McCann <mccann src gnome org>]

commit 72be6c494aa0df8bbc3f3f9137694b58e70eeee4
Author: William Jon McCann <william jon mccann gmail com>
Date:   Tue Jan 21 19:48:41 2014 -0500

    Make GTK_TREE_SORTABLE_*_SORT_COLUMN_ID defines instead of enum
    
    This allows it to be more easily documented.

 gtk/gtktreesortable.h |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)
---
diff --git a/gtk/gtktreesortable.h b/gtk/gtktreesortable.h
index c9508b5..848c2af 100644
--- a/gtk/gtktreesortable.h
+++ b/gtk/gtktreesortable.h
@@ -43,6 +43,7 @@ G_BEGIN_DECLS
  *
  * See also gtk_tree_sortable_set_sort_column_id()
  */
+#define GTK_TREE_SORTABLE_DEFAULT_SORT_COLUMN_ID (-1)
 
 /**
  * GTK_TREE_SORTABLE_UNSORTED_SORT_COLUMN_ID:
@@ -52,11 +53,7 @@ G_BEGIN_DECLS
  *
  * See also gtk_tree_sortable_set_sort_column_id()
  */
-
-enum {
-  GTK_TREE_SORTABLE_DEFAULT_SORT_COLUMN_ID = -1,
-  GTK_TREE_SORTABLE_UNSORTED_SORT_COLUMN_ID = -2
-};
+#define GTK_TREE_SORTABLE_UNSORTED_SORT_COLUMN_ID (-2)
 
 typedef struct _GtkTreeSortable      GtkTreeSortable; /* Dummy typedef */
 typedef struct _GtkTreeSortableIface GtkTreeSortableIface;