Add TA minimization: merge bisimulating states

* src/taalgos/minimize.hh, src/taalgos/minimize.cc: implements a
minimization of TA by merging bisimular states.
* src/taalgos/statessetbuilder.hh, src/taalgos/statessetbuilder.cc:
returns the set of reachable states of a TA (used in minimize.cc).
* src/taalgos/Makefile.am: add them.
* src/tgbatest/ltl2tgba.cc: add commands to test TA minimization

src/taalgos/minimize.hh

@@ -0,0 +1,36 @@
+// Copyright (C) 2009, 2010, 2011 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_TAALGOS_MINIMIZE_HH
+# define SPOT_TAALGOS_MINIMIZE_HH
+
+# include "ta/ta.hh"
+# include "ta/taexplicit.hh"
+
+namespace spot
+{
+
+  ta*
+  minimize_ta(const ta* ta_);
+
+/// @}
+}
+
+#endif /* !SPOT_TAALGOS_MINIMIZE_HH */