[gtk+] Add release note about GtkBin compatibility

[Matthias Clasen <matthiasc src gnome org>]

commit f8b66763b00eee397da4033c65440c8f5c5c5c9f
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon May 27 15:03:04 2013 -0400

    Add release note about GtkBin compatibility

 README.in |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/README.in b/README.in
index c002e11..ad50edf 100644
--- a/README.in
+++ b/README.in
@@ -87,6 +87,10 @@ Release notes for 3.10
   If you experience sizing problems with widgets in ported code,
   carefully check the expand and fill flags of your boxes.
 
+* GtkBin no longer provides default implementations for
+  get_height_for_width, subclasses now have to provide their own
+  implementation if they need height-for-width functionality.
+
 
 Release notes for 3.8
 =====================