Fix some RelaxNG violations

These are mistakes caused while translating

preface.xml

@@ -4,7 +4,7 @@
 
 <preface xml:id="preface" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://docbook.org/ns/docbook">
  <info>
-  <title>Vorwort</title>
+  <titleabbrev>Vorwort</titleabbrev>
   <title>Über dieses Handbuch</title>
   <abstract>
    <simpara>

reference/posix/functions/posix-mkfifo.xml

@@ -1,5 +1,4 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- $Revision$ -->
 <!-- EN-Revision: 265acc36ee4a1f4553a52030bf1717521c24dfb4 Maintainer: samesch Status: ready -->
 <refentry xml:id="function.posix-mkfifo" xmlns="http://docbook.org/ns/docbook">
  <refnamediv>
@@ -56,12 +55,7 @@
   </para>
  </refsect1>
 
- <refsect1 role="notes">
-  &reftitle.notes;
- </refsect1>
-
 </refentry>
-
 <!-- Keep this comment at the end of the file
 Local variables:
 mode: sgml

reference/tokenizer/reference.xml

@@ -1,9 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- $Revision$ -->
 <!-- EN-Revision: 96c9d88bad9a7d7d44bfb7f26c226df7ee9ddf26 Maintainer: nikic Status: ready -->
 
 <reference xml:id="ref.tokenizer" xmlns="http://docbook.org/ns/docbook">
- <titleabbrev>Tokenizer &Functions;</titleabbrev>
+ <title>Tokenizer &Functions;</title>
 
  &reference.tokenizer.entities.functions;