[gnome-builder] tree: use GDK_BUTTON_SECONDARY

[Christian Hergert <chergert src gnome org>]

commit d059b9a8c08c2f6affde7e416ddbfb97ec8842d5
Author: Christian Hergert <christian hergert me>
Date:   Fri Apr 10 14:51:04 2015 -0700

    tree: use GDK_BUTTON_SECONDARY

 src/tree/gb-tree.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/tree/gb-tree.c b/src/tree/gb-tree.c
index f2de741..8197919 100644
--- a/src/tree/gb-tree.c
+++ b/src/tree/gb-tree.c
@@ -823,7 +823,8 @@ gb_tree_button_press_event (GbTree         *tree,
 
   priv = tree->priv;
 
-  if ((button->type == GDK_BUTTON_PRESS) && (button->button == 3))
+  if ((button->type == GDK_BUTTON_PRESS) &&
+      (button->button == GDK_BUTTON_SECONDARY))
     {
       gtk_tree_view_get_path_at_pos (GTK_TREE_VIEW (tree),
                                      button->x,