+/** Can this requests can be executed?
+ *
+ * Most requests are always enabled but WAIT and WAITANY
+ * are not always enabled: a WAIT where the communication does not
+ * have both a source and a destination yet is not enabled
+ * (unless timeout is enabled in the wait and enabeld in SimGridMC).
+ */
+XBT_PRIVATE bool request_is_enabled(smx_simcall_t req);