+ * These is the classical producer/consumer synchronization scheme,
+ * which all concurrent programmer recode one day or another.
+ *
+ * The good thing of this implementation is that it works seamlessly
+ * in your universe. When using one of the classical simulation
+ * interface (such as MSG), it achieves the synchronization on top
+ * of the simulator. If you use instead the real life implementation
+ * comming with GRAS, it uses the synchronization of your OS
+ * (whatever could it be). The choice is done at link time.