users_guide.xml is now generated

docs/users_guide/users_guide.xml

-<?xml version="1.0" encoding="iso-8859-1"?>
-<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
-   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
-<!ENTITY % ug-ent SYSTEM "ug-ent.xml">
-%ug-ent;
-<!ENTITY ug-book SYSTEM "ug-book.xml">
-]>
-
-<book id="users-guide">
-&ug-book;
-</book>