[gtkmm] Added some comments

[Murray Cumming <murrayc src gnome org>]

commit ed5e62f317f34fcd2ee3b1c39d7ad978fda2edc2
Author: Murray Cumming <murrayc murrayc com>
Date:   Mon May 2 11:55:21 2011 +0200

    Added some comments

 gtk/src/filechooserbutton.hg |    2 +-
 gtk/src/infobar.hg           |    2 +-
 gtk/src/statusbar.hg         |    2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/gtk/src/filechooserbutton.hg b/gtk/src/filechooserbutton.hg
index 41dee58..2082b04 100644
--- a/gtk/src/filechooserbutton.hg
+++ b/gtk/src/filechooserbutton.hg
@@ -46,7 +46,7 @@ namespace Gtk
  * @ingroup Widgets
  */
 class FileChooserButton
-  : public HBox,
+  : public HBox, //Note: The C object really derives from this convenience type.
     public FileChooser
 {
   _CLASS_GTKOBJECT(FileChooserButton, GtkFileChooserButton, GTK_FILE_CHOOSER_BUTTON, Gtk::HBox, GtkHBox)
diff --git a/gtk/src/infobar.hg b/gtk/src/infobar.hg
index cc3e4f8..b9b1f03 100644
--- a/gtk/src/infobar.hg
+++ b/gtk/src/infobar.hg
@@ -51,7 +51,7 @@ namespace Gtk
  *
  * @ingroup Widgets
  */
-class InfoBar : public HBox
+class InfoBar : public HBox //Note: The C object really derives from this convenience type.
 {
   _CLASS_GTKOBJECT(InfoBar, GtkInfoBar, GTK_INFO_BAR, Gtk::HBox, GtkHBox)
 public:
diff --git a/gtk/src/statusbar.hg b/gtk/src/statusbar.hg
index f78af52..9ea7969 100644
--- a/gtk/src/statusbar.hg
+++ b/gtk/src/statusbar.hg
@@ -41,7 +41,7 @@ namespace Gtk
  *
  * @ingroup Widgets
  */
-class Statusbar : public HBox
+class Statusbar : public HBox //Note: The C object really derives from this convenience type.
 {
   _CLASS_GTKOBJECT(Statusbar,GtkStatusbar,GTK_STATUSBAR,Gtk::HBox,GtkHBox)
   _IGNORE(gtk_statusbar_push)