[gtk+] Update NEWS to mention help overlays

[Matthias Clasen <matthiasc src gnome org>]

commit 1a2cdad220a3df5cb928d285258f0278b5754b68
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Oct 21 17:15:17 2015 -0400

    Update NEWS to mention help overlays

 NEWS |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/NEWS b/NEWS
index 6459341..6a14882 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,9 @@
+Overview of Changes in GTK+ 3.19.1
+==================================
+
+* Support for help overlays to document keyboard shortcuts and gestures.
+
+
 Overview of Changes in GTK+ 3.18.1
 ==================================