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/unop.cc

@@ -0,0 +1,119 @@
+// Copyright (C) 2003, 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.
+
+#include "unop.hh"
+#include "visitor.hh"
+#include <cassert>
+
+namespace spot
+{
+  namespace ltl
+  {
+    unop::unop(type op, formula* child)
+      : op_(op), child_(child)
+    {
+      dump_ = "unop(";
+      dump_ += op_name();
+      dump_ += ", " + child->dump() + ")";
+      set_key_();
+    }
+
+    unop::~unop()
+    {
+      // Get this instance out of the instance map.
+      pair p(op(), child());
+      map::iterator i = instances.find(p);
+      assert (i != instances.end());
+      instances.erase(i);
+    }
+
+    void
+    unop::accept(visitor& v)
+    {
+      v.visit(this);
+    }
+
+    void
+    unop::accept(const_visitor& v) const
+    {
+      v.visit(this);
+    }
+
+    const formula*
+    unop::child() const
+    {
+      return child_;
+    }
+
+    formula*
+    unop::child()
+    {
+      return child_;
+    }
+
+    unop::type
+    unop::op() const
+    {
+      return op_;
+    }
+
+    const char*
+    unop::op_name() const
+    {
+      switch (op_)
+	{
+	case Not:
+	  return "Not";
+	case X:
+	  return "X";
+	case F:
+	  return "F";
+	case G:
+	  return "G";
+	}
+      // Unreachable code.
+      assert(0);
+      return 0;
+    }
+
+    unop::map unop::instances;
+
+    unop*
+    unop::instance(type op, formula* child)
+    {
+      pair p(op, child);
+      map::iterator i = instances.find(p);
+      if (i != instances.end())
+	{
+	  return static_cast<unop*>(i->second->ref());
+	}
+      unop* ap = new unop(op, child);
+      instances[p] = ap;
+      return static_cast<unop*>(ap->ref());
+    }
+
+    unsigned
+    unop::instance_count()
+    {
+      return instances.size();
+    }
+  }
+}