[gnome-terminal] notebook: Add ifdef for gtk+ < 3.16

[Christian Persch <chpe src gnome org>]

commit 0f3e02d18112c4b4cc28826b7df98766681c5253
Author: Christian Persch <chpe gnome org>
Date:   Fri Aug 28 18:29:07 2015 +0200

    notebook: Add ifdef for gtk+ < 3.16
    
    https://bugzilla.gnome.org/show_bug.cgi?id=754254

 src/terminal-notebook.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/terminal-notebook.c b/src/terminal-notebook.c
index efd5343..d6c9dd1 100644
--- a/src/terminal-notebook.c
+++ b/src/terminal-notebook.c
@@ -68,7 +68,9 @@ update_tab_visibility (TerminalNotebook *notebook,
     show_tabs = (gtk_notebook_get_n_pages (gtk_notebook) + change) > 1;
     break;
   case GTK_POLICY_NEVER:
+#if GTK_CHECK_VERSION (3, 16, 0)
   case GTK_POLICY_EXTERNAL:
+#endif
   default:
     show_tabs = FALSE;
     break;