[gtkmm] Update some TODO comments

[Murray Cumming <murrayc src gnome org>]

commit 63020565a9a47a1e2aa13c76af0a886c15cbd9c5
Author: Murray Cumming <murrayc murrayc com>
Date:   Wed Oct 9 10:27:18 2013 +0200

    Update some TODO comments

 gdk/src/rgba.hg        |    2 +-
 gtk/src/actiongroup.hg |    3 ++-
 gtk/src/celllayout.hg  |    2 +-
 3 files changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/gdk/src/rgba.hg b/gdk/src/rgba.hg
index e309076..86b1424 100644
--- a/gdk/src/rgba.hg
+++ b/gdk/src/rgba.hg
@@ -17,7 +17,7 @@
  */
 
 #include <glibmm/value.h>
-#include <gdk/gdk.h> //TODO: Remove this?
+#include <gdk/gdk.h> //Needed for our RGBATraits here.
 
 _DEFS(gdkmm,gdk)
 
diff --git a/gtk/src/actiongroup.hg b/gtk/src/actiongroup.hg
index 54fef95..a109b79 100644
--- a/gtk/src/actiongroup.hg
+++ b/gtk/src/actiongroup.hg
@@ -86,7 +86,8 @@ public:
   void add(const Glib::RefPtr<Action>& action, const AccelKey& accel_key, const Action::SlotActivate& slot);
   _WRAP_METHOD(void remove(const Glib::RefPtr<Action>& action), gtk_action_group_remove_action)
 
-   //TODO: We probably need to use this in our add_actions() implementation:
+   //TODO: We probably need to use this in our add_actions() implementation.
+   //But this whole class will be deprecated soon anyway.
   _WRAP_METHOD(Glib::ustring translate_string(const Glib::ustring& string) const, 
gtk_action_group_translate_string)
 
 
diff --git a/gtk/src/celllayout.hg b/gtk/src/celllayout.hg
index 8aa5260..bfe2bf2 100644
--- a/gtk/src/celllayout.hg
+++ b/gtk/src/celllayout.hg
@@ -103,7 +103,7 @@ protected:
 #m4 _CONVERSION(`const char*',`const Glib::ustring&',__GCHARP_TO_USTRING)
   _WRAP_VFUNC(void add_attribute(CellRenderer* cell, const Glib::ustring& attribute, int column), 
add_attribute)
 
-//TODO (added in GTK+ 2.4):  _WRAP_VFUNC(void set_cell_data_func(CellRenderer* cell, GtkCellLayoutDataFunc 
func, gpointer func_data, GDestroyNotify destroy), gtk_cell_layout_set_cell_data_func)
+//TODO when we can break ABI(added in GTK+ 2.4):  _WRAP_VFUNC(void set_cell_data_func(CellRenderer* cell, 
GtkCellLayoutDataFunc func, gpointer func_data, GDestroyNotify destroy), gtk_cell_layout_set_cell_data_func)
   _WRAP_VFUNC(void clear_attributes(CellRenderer* cell), clear_attributes)
   _WRAP_VFUNC(void reorder(CellRenderer* cell, int position), reorder)