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

@@ -1081,11 +1081,11 @@
 
                                 len = strlen(func_strs[MODE]);
                                 if ((strncmp(str, func_strs[MODE], len) == 0) &&
                                     (*(str+(len)) == '=')) {
                                     for (str = (str+(++len)), i = 0;
-                                        *str != NULL; i++, str++) {
+                                        *str != '\0'; i++, str++) {
                                                 buf[i] = *str;
 
                                     }
                                 }
                                 buf[i] = '\0';

@@ -1279,19 +1279,19 @@
         DBG(1, ("find_physical_slot_names\n"));
 
         if ((root_node = di_init("/", DINFOCPYALL|DINFOPATH))
                 == DI_NODE_NIL) {
                 DBG(1, ("di_init() failed\n"));
-                return (NULL);
+                return (0);
         }
 
         slotarg->devpath = (char *)devcomp;
 
         if ((slotarg->promp = di_prom_init()) == DI_PROM_HANDLE_NIL) {
                 DBG(1, ("di_prom_init() failed\n"));
                 di_fini(root_node);
-                return (NULL);
+                return (0);
         }
 
         (void) di_walk_minor(root_node, "ddi_ctl:attachment_point:pci",
                 0, (void *)slotarg, find_slotname);