[gtk+] docs: Add a missing Since: tag

[Matthias Clasen <matthiasc src gnome org>]

commit 8d3a91d6ba101d7d78e7a340a50c2cee4d524f6c
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Dec 5 09:08:35 2013 -0500

    docs: Add a missing Since: tag

 gtk/gtkdnd.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkdnd.c b/gtk/gtkdnd.c
index 2f70465..769693e 100644
--- a/gtk/gtkdnd.c
+++ b/gtk/gtkdnd.c
@@ -2695,6 +2695,8 @@ gtk_drag_begin_internal (GtkWidget         *widget,
  * If you can really not pass a real event, pass #NULL instead.
  *
  * Return value: (transfer none): the context for this drag.
+ *
+ * Since: 3.10
  **/
 GdkDragContext *
 gtk_drag_begin_with_coordinates (GtkWidget         *widget,