[libxml++] Added a TODO for when we can break ABI

[Murray Cumming <murrayc src gnome org>]

commit 062c7416b435e1e68cf9acf1f542bbb4ab90587e
Author: Murray Cumming <murrayc murrayc com>
Date:   Tue Oct 19 09:35:40 2010 +0200

    Added a TODO for when we can break ABI

 libxml++/document.h |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)
---
diff --git a/libxml++/document.h b/libxml++/document.h
index 826dc14..70f282c 100644
--- a/libxml++/document.h
+++ b/libxml++/document.h
@@ -25,7 +25,7 @@ extern "C" {
 }
 #endif //DOXYGEN_SHOULD_SKIP_THIS
 
-namespace xmlpp 
+namespace xmlpp
 {
 
 typedef enum {
@@ -62,17 +62,18 @@ class Document : NonCopyable
 public:
   explicit Document(const Glib::ustring& version = "1.0");
   virtual ~Document();
-  
+
   /** @return The encoding used in the source from which the document has been loaded.
     */
   Glib::ustring get_encoding() const;
-  
+
   Dtd* get_internal_subset() const;
-  
+
   void set_internal_subset(const Glib::ustring& name,
                            const Glib::ustring& external_id,
                            const Glib::ustring& system_id);
 
+  //TODO: There should be a const and non-const version.
   /** Return the root node.
    * This function does _not_ create a default root node if it doesn't exist.
    * @return A pointer to the root node if it exists, 0 otherwise.