Added XML comment to the DTD emphasizing that this DTD is for

OpenOffice.org 1.x XML Documents and is not a DTD for any ODF
document.  See Apache OpenOffice bugzilla issue #49853.

xmloff/dtd/office.dtd

 <?xml version="1.0" encoding="UTF-8"?>
 <!--***********************************************************
- * 
+ *
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
@@ -8,19 +8,29 @@
  * to you under the Apache License, Version 2.0 (the
  * "License"); you may not use this file except in compliance
  * with the License.  You may obtain a copy of the License at
- * 
+ *
  *   http://www.apache.org/licenses/LICENSE-2.0
- * 
+ *
  * Unless required by applicable law or agreed to in writing,
  * software distributed under the License is distributed on an
  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
  * KIND, either express or implied.  See the License for the
  * specific language governing permissions and limitations
  * under the License.
- * 
+ *
  ***********************************************************-->
 
+<!-- This DTD and the entities it includes are for the
+     XML document format produced by OpenOffice.org 1.x.
 
+     This DTD is for reference from the XML prolog of documents
+     in that OpenOffice.org 1.x format.  It can be used for the
+     DTD validation of those XML documents.
+
+     This DTD is not applicable to ODF documents.  ODF support
+     began in OpenOffice.org 2.x releases.  ODF XML documents
+     have Relax NG Schemas.
+     -->
 
 <!ENTITY % dtypes-mod SYSTEM "dtypes.mod">
 %dtypes-mod;