Replace spot::ltl_file by a rewritten spot::ltl::ltl_file.

* src/tgba/tgbafromfile.cc, src/tgba/tgbafromfile.hh: Delete these
files.
* src/tgba/Makefile.am: Remove them.
* src/ltl/ltlparse/ltlfile.hh, src/ltl/ltlparse/ltlfile.cc: New
files.
* src/ltl/ltlparse/Makefile.am: Add them.
* bench/scc-stats/stats.cc, bench/split-product/cutscc.cc: Rewrite
using the new class.

src/ltlparse/ltlfile.hh

@@ -0,0 +1,48 @@
+// Copyright (C) 2010 Laboratoire de Recherche et Développement
+// de l'Epita (LRDE).
+//
+// 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.
+
+#ifndef SPOT_LTLPARSE_LTLFILE_HH
+# define SPOT_LTLPARSE_LTLFILE_HH
+#include <fstream>
+#include "ltlast/formula.hh"
+
+
+namespace spot
+{
+  namespace ltl
+  {
+
+    /// \brief Read LTL formulae from a file, one by one
+    /// \ingroup ltl_io
+    class ltl_file
+    {
+    public:
+      ltl_file(const std::string& filename);
+      ltl_file(const char* filename);
+      /// Return the next parsed LTL formula, and 0 at end of file.
+      formula* next();
+    private:
+      std::ifstream in;
+    };
+
+  }
+}
+
+#endif