[gtkmm] Mark the branch in the ChangeLog

[Murray Cumming <murrayc src gnome org>]

commit 2fae4a5336b45810eb46ed41c295951ab9c93b5b
Author: Murray Cumming <murrayc murrayc com>
Date:   Mon Oct 10 20:17:21 2011 +0200

    Mark the branch in the ChangeLog

 ChangeLog |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/ChangeLog b/ChangeLog
index b15ef56..1a395d8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -4,6 +4,8 @@
 
 	* gtk/src/dialog.hg: Insert 'constversion' in get_vbox() const, because
 	a bug in gmmproc has been fixed in glibmm 2.29.13. Bug #657751, comment 8.
+	
+This is the master branch, for gtkmm 3.3/4. See also the gtkmm-3-2 branch.
 
 3.2.0: