Bug Fixes - Att, Subst

- Fixed but that required all known attributes to be listed by name
  in order to be recognized by creating new Att::validInternalName
  method.
- Fixed bug in non-global Subst that failed to save a modified
  annotation.

src/Att.h

@@ -44,6 +44,7 @@ public:
   ~Att ();
 
   bool valid (const std::string&) const;
+  static bool validInternalName (const std::string&);
   static bool validModifiableName (const std::string&);
   static bool validNameValue (const std::string&, const std::string&, const std::string&);
   static bool validNameValue (std::string&, std::string&, std::string&);