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

@@ -300,23 +300,23 @@
                 if (t_getstate(fd) != T_DATAXFER)
                         return (FAIL);
         }
 
         if (info.tsdu <= 0 || nbytes <= info.tsdu)
-                return (t_snd(fd, buf, nbytes, NULL));
+                return (t_snd(fd, buf, nbytes, 0));
 
         /* if get here, then there is a limit on transmit size  */
         /* (info.tsdu > 0) and buf exceeds it                   */
         i = ret = 0;
         while (nbytes >= info.tsdu) {
-                if ((ret = t_snd(fd,  &buf[i], info.tsdu, NULL)) != info.tsdu)
+                if ((ret = t_snd(fd,  &buf[i], info.tsdu, 0)) != info.tsdu)
                         return ((ret >= 0 ? (i + ret) : ret));
                 i += info.tsdu;
                 nbytes -= info.tsdu;
         }
         if (nbytes != 0) {
-                if ((ret = t_snd(fd,  &buf[i], nbytes, NULL)) != nbytes)
+                if ((ret = t_snd(fd,  &buf[i], nbytes, 0)) != nbytes)
                         return ((ssize_t)(ret >= 0 ? (i + ret) : ret));
                 i += nbytes;
         }
         return ((ssize_t)i);
 }