[glibmm] Added a TODO

[Murray Cumming <murrayc src gnome org>]

commit 5c4a0d45e3d1961fd7c5ff8ce65d9493c3a5e9c2
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Nov 4 14:52:45 2010 +0100

    Added a TODO

 glib/glibmm/main.h |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/glib/glibmm/main.h b/glib/glibmm/main.h
index 5d2acdf..1905344 100644
--- a/glib/glibmm/main.h
+++ b/glib/glibmm/main.h
@@ -740,7 +740,9 @@ protected:
   virtual bool dispatch(sigc::slot_base* slot);
 
 private:
+  //TODO: Replace with gint64, because TimeVal is deprecated, when we can break ABI.
   Glib::TimeVal expiration_;
+
   unsigned int  interval_;
 };