kdc: support for PAC_ATTRIBUTES_INFO

Add PAC_ATTRIBUTES_INFO to the PAC. This info buffer indicates whether the user
explicitly requested a PAC be present or absent.

Note: this changes the windc plugin ABI.

tests/plugin/windc.c

@@ -23,13 +23,14 @@ pac_generate(void *ctx, krb5_context context,
 	     struct hdb_entry_ex *client,
 	     struct hdb_entry_ex *server,
 	     const krb5_keyblock *pk_replykey,
-	     const krb5_boolean *pac_request,
+	     uint64_t pac_attributes,
 	     krb5_pac *pac)
 {
     krb5_error_code ret;
     krb5_data data;
 
-    if (pac_request != NULL && *pac_request == FALSE) {
+    if ((pac_attributes & (KRB5_PAC_WAS_REQUESTED |
+			   KRB5_PAC_WAS_GIVEN_IMPLICITLY)) == 0) {
 	*pac = NULL;
 	return 0;
     }