Declare the sba class in its own header.

* src/tgba/sba.hh: New file, extrated from...
* src/tgba/tgbaexplicit.hh: ... here.  Also rename
sba_explicit::is_accepting as sba_explicit::state_is_accepting for
consistency with tgba_sba_proxy.
* src/tgbatest/explicit2.cc: Adjust to the renaming.
* src/tgba/Makefile.am: Add sba.hh.

src/tgba/sba.hh

@@ -0,0 +1,45 @@
+// Copyright (C) 2012 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_TGBA_SBA_HH
+# define SPOT_TGBA_SBA_HH
+
+#include "tgba.hh"
+
+namespace spot
+{
+  /// \brief A State-based Generalized Büchi Automaton.
+  /// \ingroup tgba_essentials
+  ///
+  /// An SBA is a TGBA in which the outgoing transitions of
+  /// a state are either all accepting (in which case the
+  /// source state is said "accepting"(, or all non-accepting.
+  class sba: public tgba
+  {
+  public:
+    /// \brief is \a s an accepting state?
+    ///
+    /// If a state is accepting all its outgoing transitions are
+    /// accepting.
+    virtual bool state_is_accepting(const spot::state* s) const = 0;
+  };
+}
+
+#endif // SPOT_TGBA_SBA_HH