add property for toekn-ring example

examples/token-o1.if

+/*
+ *
+ * IF-Toolset - Copyright (C) UGA - CNRS - G-INP
+ *
+ * by  Marius  -  Iulian  -  Susanne  -  Laurent  -   Joseph
+ *       Bozga  -    Ober  -     Graf  -  Mounier  -   Sifakis
+ * 
+ * This  software is  a computer  program whose  purpose is  to simulate,
+ * explore and model-check  real-time systems represented using  the IF -
+ * intermediate  format  -  language.   This  software  package  contains
+ * sources,  documentation,  and  examples.
+ * 
+ * This software is governed by the CeCILL-B license under French law and
+ * abiding by the  rules of distribution of free software.   You can use,
+ * modify  and/ or  redistribute  the  software under  the  terms of  the
+ * CeCILL-B license as circulated by CEA, CNRS and INRIA at the following
+ * URL "http://www.cecill.info".
+ *
+ * As a counterpart to the access to  the source code and rights to copy,
+ * modify and  redistribute granted  by the  license, users  are provided
+ * only with a limited warranty and  the software's author, the holder of
+ * the economic  rights, and the  successive licensors have  only limited
+ * liability.
+ *
+ * In this respect, the user's attention is drawn to the risks associated
+ * with loading,  using, modifying  and/or developing or  reproducing the
+ * software by the user in light of its specific status of free software, 
+ * that may  mean that  it is  complicated to  manipulate, and  that also
+ * therefore means  that it  is reserved  for developers  and experienced
+ * professionals having in-depth computer  knowledge. Users are therefore
+ * encouraged  to load  and test  the software's  suitability as  regards
+ * their  requirements  in  conditions  enabling the  security  of  their
+ * systems and/or  data to  be ensured  and, more  generally, to  use and
+ * operate it in the same conditions as regards security.
+ * 
+ * The fact that  you are presently reading this means  that you have had
+ * knowledge of the CeCILL-B license and that you accept its terms.
+ *
+ */
+
+pure observer o1;
+
+state wait #start ;
+  match output token();
+    nextstate done;
+endstate;
+
+state done #success ;
+endstate;
+
+endobserver;