Add an administrative domain to the passwd/group cache key for

AIX which can have different name <-> ID mappings depending
on whether the database is local, LDAP, etc.

plugins/sudoers/pwutil.h

@@ -24,6 +24,7 @@
  */
 struct cache_item {
     unsigned int refcnt;
+    char registry[16];
     /* key */
     union {
 	uid_t uid;