IKEv1 XAuth: Added new MIGRATE status type to status_t.

When a task returns this status from a build or process method, it is a signal to the task manager that it should treat it as if the task returned SUCCESS.
  Additionally it will migrate all remaining tasks from the current queue to a different one, calling swap_initiator for each applicable task.
  Finally, the task manager will call "initiate", if applicable, to kick off tasks in the "queued_tasks" queue.
  Task queue relocation mapping:
	  passive_tasks moves to queued_tasks (which is then fed to active by the initiate call).
	  active_tasks moves to passive_tasks

src/libstrongswan/utils.h

@@ -299,6 +299,12 @@ enum status_t {
 	 * Another call to the method is required.
 	 */
 	NEED_MORE,
+
+	/**
+	 * For tasks only, same as SUCCESS, but also migrate all remaining tasks
+	 * in the current queue to the opposite queue (passive->active or active->passive)
+	 */
+	MIGRATE,
 };
 
 /**