lib/krb5: add krb5_mk_error_ext() helper function

This gives the caller the ability to skip the client_name
and only provide client_realm. This is required for
KDC_ERR_WRONG_REALM messages.

Signed-off-by: Stefan Metzmacher <metze@samba.org>

lib/krb5/version-script.map

@@ -433,6 +433,7 @@ HEIMDAL_KRB5_2.0 {
 		krb5_make_principal;
 		krb5_max_sockaddr_size;
 		krb5_mk_error;
+		krb5_mk_error_ext;
 		krb5_mk_priv;
 		krb5_mk_rep;
 		krb5_mk_req;