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

@@ -427,11 +427,11 @@
                                     mcnode);
                         }
                 }
         }
 
-        return (NULL);
+        return (0);
 }
 
 int
 mc_node_create(topo_mod_t *mod, uint16_t chip_smbid, tnode_t *pnode,
     const char *name, nvlist_t *auth)

@@ -449,24 +449,24 @@
                 whinge(mod, NULL, "mc failed to snapshot %s\n",
                     strerror(errno));
 
                 free(buf);
                 (void) close(mc_fd);
-                return (NULL);
+                return (0);
         }
         (void) close(mc_fd);
         (void) nvlist_unpack(buf, mcs.mcs_size, &nvl, 0);
         topo_mod_free(mod, buf, mcs.mcs_size);
 
         if (nvlist_lookup_uint8(nvl, MCINTEL_NVLIST_VERSTR, &ver) != 0) {
                 whinge(mod, NULL, "mc nvlist is not versioned\n");
                 nvlist_free(nvl);
-                return (NULL);
+                return (0);
         } else if (ver != MCINTEL_NVLIST_VERS0) {
                 whinge(mod, NULL, "mc nvlist version mismatch\n");
                 nvlist_free(nvl);
-                return (NULL);
+                return (0);
         }
 
         rc = mc_nb_create(mod, chip_smbid, pnode, name, auth, nvl);
 
         nvlist_free(nvl);