[gtksourceview] docs: fix a GTK-Doc warning about a missing link

[Sébastien Wilmet <swilmet src gnome org>]

commit ecc5ad8c8ee4b7e74ca25d56c5c7f823c0930a1a
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sat Aug 8 21:51:52 2015 +0200

    docs: fix a GTK-Doc warning about a missing link
    
    The warning:
    
    html/GtkSourceStyleScheme.html:157: warning: no link for:
    'style-reference' -> (style scheme reference).
    
    Adding the doctypes fixes the problem. Change also the part to a
    chapter, since a part is not needed.

 docs/reference/gtksourceview-docs.xml |    4 ++--
 docs/reference/lang-reference.xml     |    8 ++++++++
 docs/reference/lang-tutorial.xml      |    8 ++++++++
 docs/reference/style-reference.xml    |    8 ++++++++
 4 files changed, 26 insertions(+), 2 deletions(-)
---
diff --git a/docs/reference/gtksourceview-docs.xml b/docs/reference/gtksourceview-docs.xml
index 2a9b91c..054e932 100644
--- a/docs/reference/gtksourceview-docs.xml
+++ b/docs/reference/gtksourceview-docs.xml
@@ -81,12 +81,12 @@
     </chapter>
   </part>
 
-  <part>
+  <chapter>
     <title>Syntax highlighting reference</title>
     <xi:include href="lang-tutorial.xml"/>
     <xi:include href="lang-reference.xml"/>
     <xi:include href="style-reference.xml"/>
-  </part>
+  </chapter>
 
   <chapter id="object-tree">
     <title>Object Hierarchy</title>
diff --git a/docs/reference/lang-reference.xml b/docs/reference/lang-reference.xml
index 383c22a..db1c52b 100644
--- a/docs/reference/lang-reference.xml
+++ b/docs/reference/lang-reference.xml
@@ -1,3 +1,11 @@
+<?xml version="1.0"?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
+   "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd";
+[
+ <!ENTITY % local.common.attrib "xmlns:xi CDATA #FIXED 'http://www.w3.org/2003/XInclude'">
+ <!ENTITY % gtkdocentities SYSTEM "xml/gtkdocentities.ent">
+ %gtkdocentities;
+]>
 <refentry id="lang-reference" revision="6 March 2015">
 <refmeta>
 <refentrytitle>Language Definition v2.0 Reference</refentrytitle>
diff --git a/docs/reference/lang-tutorial.xml b/docs/reference/lang-tutorial.xml
index 0631b21..60f7991 100644
--- a/docs/reference/lang-tutorial.xml
+++ b/docs/reference/lang-tutorial.xml
@@ -1,3 +1,11 @@
+<?xml version="1.0"?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
+   "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd";
+[
+ <!ENTITY % local.common.attrib "xmlns:xi CDATA #FIXED 'http://www.w3.org/2003/XInclude'">
+ <!ENTITY % gtkdocentities SYSTEM "xml/gtkdocentities.ent">
+ %gtkdocentities;
+]>
 <refentry id="lang-tutorial" revision="5 May 2005">
 <refmeta>
 <refentrytitle>Language Definition v2.0 Tutorial</refentrytitle>
diff --git a/docs/reference/style-reference.xml b/docs/reference/style-reference.xml
index 452e7ea..7b2d4af 100644
--- a/docs/reference/style-reference.xml
+++ b/docs/reference/style-reference.xml
@@ -1,3 +1,11 @@
+<?xml version="1.0"?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
+   "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd";
+[
+ <!ENTITY % local.common.attrib "xmlns:xi CDATA #FIXED 'http://www.w3.org/2003/XInclude'">
+ <!ENTITY % gtkdocentities SYSTEM "xml/gtkdocentities.ent">
+ %gtkdocentities;
+]>
 <refentry id="style-reference" revision="6 October 2013">
 <refmeta>
 <refentrytitle>Style Scheme Definition Reference</refentrytitle>