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

@@ -348,11 +348,11 @@
         { "ip", TIO_ATTR_STR, &termio_info.ti_ip },
         { "clear", TIO_ATTR_STR, &termio_info.ti_clear },
         { "cnorm", TIO_ATTR_STR, &termio_info.ti_cnorm },
         { "nel", TIO_ATTR_STR, &termio_info.ti_nel },
         { "cr", TIO_ATTR_STR, &termio_info.ti_cr },
-        { NULL, NULL, NULL }
+        { NULL, 0, NULL }
 };
 
 /*
  * One-key accelerators.  Some commands are used so frequently as to need
  * single-key equivalents.  termio_accelkeys contains a list of the accelerator