[gtkmm] Add TODO comments to derive from Actionable when we can break ABI.

[Murray Cumming <murrayc src gnome org>]

commit 3381c0aea10891a2dccc49b5e450fd497a3cb807
Author: Murray Cumming <murrayc murrayc com>
Date:   Thu Sep 26 13:17:41 2013 +0200

    Add TODO comments to derive from Actionable when we can break ABI.
    
    * gtk/src/button.hg:
    * gtk/src/menuitem.hg:
    * gtk/src/switch.hg:
    * gtk/src/toolbutton.hg: These classes need to derive from
      Gtk::Actionable so we can, for instance, call
      set_action_name() on them to use them with a Gio::Action that
      is in an action group.
      However, we cannot do this without breaking ABI.

 gtk/src/button.hg     |    2 ++
 gtk/src/menuitem.hg   |    2 ++
 gtk/src/switch.hg     |    2 ++
 gtk/src/toolbutton.hg |    2 ++
 4 files changed, 8 insertions(+), 0 deletions(-)
---
diff --git a/gtk/src/button.hg b/gtk/src/button.hg
index 00e52d6..c709b57 100644
--- a/gtk/src/button.hg
+++ b/gtk/src/button.hg
@@ -32,6 +32,8 @@ namespace Gtk
 
 namespace Stock { struct BuiltinStockID; }
 
+//TODO: Derive from (and implement) Actionable when we can break ABI.
+
 /** A widget that creates a signal when clicked on.
  *
  * This widget is generally used with a signal handler that is called when the button is pressed.
diff --git a/gtk/src/menuitem.hg b/gtk/src/menuitem.hg
index 041d1fe..f605fda 100644
--- a/gtk/src/menuitem.hg
+++ b/gtk/src/menuitem.hg
@@ -33,6 +33,8 @@ _PINCLUDE(gtkmm/private/bin_p.h)
 namespace Gtk
 {
 
+//TODO: Derive from (and implement) Actionable when we can break ABI.
+
 class Menu;
 namespace Menu_Helpers { class Element; }
 
diff --git a/gtk/src/switch.hg b/gtk/src/switch.hg
index c4e5c64..1247827 100644
--- a/gtk/src/switch.hg
+++ b/gtk/src/switch.hg
@@ -23,6 +23,8 @@ _PINCLUDE(gtkmm/private/widget_p.h)
 namespace Gtk
 {
 
+//TODO: Derive from (and implement) Actionable when we can break ABI.
+
 /** A "light switch"-style toggle.
  *
  * The Switch widget has two states: on or off. The user can control
diff --git a/gtk/src/toolbutton.hg b/gtk/src/toolbutton.hg
index e2f4e0c..581ff43 100644
--- a/gtk/src/toolbutton.hg
+++ b/gtk/src/toolbutton.hg
@@ -28,6 +28,8 @@ _PINCLUDE(gtkmm/private/toolitem_p.h)
 namespace Gtk
 {
 
+//TODO: Derive from (and implement) Actionable when we can break ABI.
+
 /** A Gtk::ToolItem subclass that displays buttons.
  *
  * A ToolButton is are Gtk::ToolItem containing a button.