5218 posix definition of NULL
correct unistd.h and iso/stddef_iso.h
update gate source affected

*** 230,240 ****
          (void) init_channel();
  
          (void) mutex_init(&evq_lock, USYNC_THREAD, NULL);
          (void) cond_init(&evq_cv, USYNC_THREAD, NULL);
  
!         if (thr_create(NULL, NULL, (void *(*)(void *))subscriber_deliver_thr,
              NULL, 0, &deliver_thr_id) != 0) {
                  syseventd_err_print(INIT_SUB_THR_CREATE_ERR, strerror(errno));
                  return (NULL);
          }
  
--- 230,240 ----
          (void) init_channel();
  
          (void) mutex_init(&evq_lock, USYNC_THREAD, NULL);
          (void) cond_init(&evq_cv, USYNC_THREAD, NULL);
  
!         if (thr_create(NULL, 0, (void *(*)(void *))subscriber_deliver_thr,
              NULL, 0, &deliver_thr_id) != 0) {
                  syseventd_err_print(INIT_SUB_THR_CREATE_ERR, strerror(errno));
                  return (NULL);
          }