ltsmin: remove ltdl from public headers

* spot/ltsmin/Makefile.am,
spot/ltsmin/spins_interface.cc,
spot/ltsmin/spins_interface.hh: here.

spot/ltsmin/spins_interface.cc

@@ -0,0 +1,32 @@
+// -*- coding: utf-8 -*-
+// Copyright (C) 2017 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 3 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
+#include <spot/ltsmin/spins_interface.hh>
+#include <ltdl.h>
+
+namespace spot
+{
+  spins_interface::~spins_interface()
+  {
+    lt_dlhandle h = (lt_dlhandle) handle;
+    if (h)
+      lt_dlclose(h);
+    lt_dlexit();
+  }
+}