Add a new task type for the drifting of sparts.

src/task.c

@@ -61,6 +61,7 @@ const char *taskID_names[task_type_count] = {"none",
                                              "ghost_out",
                                              "extra_ghost",
                                              "drift_part",
+					     "drift_spart",
                                              "drift_gpart",
                                              "drift_gpart_out",
                                              "end_force",

src/task.h

@@ -52,6 +52,7 @@ enum task_types {
   task_type_ghost_out, /* Implicit */
   task_type_extra_ghost,
   task_type_drift_part,
+  task_type_drift_spart,
   task_type_drift_gpart,
   task_type_drift_gpart_out, /* Implicit */
   task_type_end_force,