Use struct berval DNs for root DN and update DN

servers/slapd/add.c

servers/slapd/back-bdb/add.c

servers/slapd/back-bdb/delete.c

servers/slapd/back-bdb/modrdn.c

servers/slapd/back-ldbm/add.c

servers/slapd/back-ldbm/delete.c

servers/slapd/back-ldbm/modrdn.c

servers/slapd/backend.c

servers/slapd/config.c

servers/slapd/delete.c

servers/slapd/modify.c

servers/slapd/modrdn.c

servers/slapd/passwd.c

servers/slapd/proto-slap.h

servers/slapd/repl.c

servers/slapd/slap.h