[gtkmm-documentation] Added a comment.

[Murray Cumming <murrayc src gnome org>]

commit f58294d41611dca708fc1faf9146d1eb9161fe80
Author: Murray Cumming <murrayc murrayc com>
Date:   Sat Sep 12 13:34:47 2009 +0200

    Added a comment.

 docs/tutorial/C/gtkmm-tutorial-in.xml |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/docs/tutorial/C/gtkmm-tutorial-in.xml b/docs/tutorial/C/gtkmm-tutorial-in.xml
index 3a92d6c..436a67e 100644
--- a/docs/tutorial/C/gtkmm-tutorial-in.xml
+++ b/docs/tutorial/C/gtkmm-tutorial-in.xml
@@ -28,6 +28,7 @@ desired (e.g. boldface, monospace, etc) to make it stand out as the project
 name
 -->
 
+<!-- The XSL for library.gnome.org requires this id. -->
 <book id="index">
 
   <bookinfo>