[gtk+/wip/overlay-scrollbar] Add a since

[Matthias Clasen <matthiasc src gnome org>]

commit 733fd6a8c4e7140eb6600bb096c0f75a8a5ac917
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Oct 7 23:15:27 2014 -0400

    Add a since

 gtk/gtkscrolledwindow.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkscrolledwindow.h b/gtk/gtkscrolledwindow.h
index 7d6ce94..780696d 100644
--- a/gtk/gtkscrolledwindow.h
+++ b/gtk/gtkscrolledwindow.h
@@ -128,7 +128,7 @@ typedef enum
  *  content determines the size.
  * @GTK_POLICY_EXTERNAL: Don't show a scrollbar, but don't force the
  *  size to follow the content. This can be used e.g. to make multiple
- *  scrolled windows share a scrollbar.
+ *  scrolled windows share a scrollbar. Since: 3.16
  *
  * Determines how the size should be computed to achieve the one of the
  * visibility mode for the scrollbars.