compel: Add compel_stop_task() to UAPI headers

The routine itself is in library, just forgot to putt the
declaration into UAPI header.
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

compel/include/uapi/infect.h

@@ -25,6 +25,8 @@ struct seize_task_status {
 extern int compel_wait_task(int pid, int ppid,
 		int (*get_status)(int pid, struct seize_task_status *),
 		struct seize_task_status *st);
+
+extern int compel_stop_task(int pid);
 extern int compel_unseize_task(pid_t pid, int orig_state, int state);
 
 /*