Revert everything related to Damien's work in 2008 (he will commit a new version soon).

Here are the reverted patches:
8c0d1003b0,
25a3114287,
9afbaf6342,
dc0005f4e1,
543190f2bc.

src/ltlast/refformula.hh

@@ -0,0 +1,52 @@
+// Copyright (C) 2003, 2004, 2005  Laboratoire d'Informatique de Paris 6 (LIP6),
+// département Systèmes Répartis Coopératifs (SRC), Université Pierre
+// et Marie Curie.
+//
+// This file is part of Spot, a model checking library.
+//
+// Spot is free software; you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// Spot is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+// License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Spot; see the file COPYING.  If not, write to the Free
+// Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+// 02111-1307, USA.
+
+/// \file ltlast/refformula.hh
+/// \brief Reference-counted LTL formulae
+#ifndef SPOT_LTLAST_REFFORMULA_HH
+# define SPOT_LTLAST_REFFORMULA_HH
+
+#include "formula.hh"
+
+namespace spot
+{
+  namespace ltl
+  {
+
+    /// \brief A reference-counted LTL formula.
+    /// \ingroup ltl_ast
+    class ref_formula : public formula
+    {
+    protected:
+      virtual ~ref_formula();
+      ref_formula();
+      void ref_();
+      bool unref_();
+      /// Number of references to this formula.
+      unsigned ref_count_();
+    private:
+      unsigned ref_counter_;
+    };
+
+  }
+}
+
+#endif // SPOT_LTLAST_REFFORMULA_HH