[gtkmm] NEWS: Mention changes for the next API-adding release.

[Murray Cumming <murrayc src gnome org>]

commit e18bdad551ceba0f90b888625cd427f2e2cb0249
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Mar 25 11:17:29 2015 +0100

    NEWS: Mention changes for the next API-adding release.
    
    So we remember to mention them. These just missed the 3.16.0 release.

 NEWS |   10 ++++++++++
 1 files changed, 10 insertions(+), 0 deletions(-)
---
diff --git a/NEWS b/NEWS
index 814f278..b4ed44d 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,13 @@
+TODO: 3.17.1 (unstable):
+
+Gdk:
+* Deprecate open_default_libgtk_only() and supports_composite().
+* Window: Deprecate get/set_composited(), set_static_gravities() and flush().
+
+Gtk:
+* CellRendererPixbuf: Deprecate property_follow_state().
+
+
 3.16:
 
 API additions since 3.14: