Update to Devhelp index file format version 2

Fixes #89

doc/devhelp/libxml2.devhelp

diff --git a/doc/devhelp/libxml2.devhelp b/doc/devhelp/libxml2.devhelp
index 2e8eab3..51b6f26 100644
--- a/doc/devhelp/libxml2.devhelp
+++ b/doc/devhelp/libxml2.devhelp
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<book xmlns="http://www.devhelp.net/book" title="libxml2 Reference Manual" link="index.html" author="" name="libxml2">
+<book xmlns="http://www.devhelp.net/book" title="libxml2 Reference Manual" link="index.html" version="2" author="" name="libxml2">
   <chapters>
     <sub name="API" link="general.html">
       <sub name="DOCBparser" link="libxml2-DOCBparser.html"/>

doc/html/libxml.devhelp

diff --git a/doc/html/libxml.devhelp b/doc/html/libxml.devhelp
index 006b4bf..d26d4d8 100644
--- a/doc/html/libxml.devhelp
+++ b/doc/html/libxml.devhelp
@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<book xmlns="http://www.devhelp.net/book" title="Gnome XML Library Reference Manual " link="index.html" author="" name="libxml">
+<book xmlns="http://www.devhelp.net/book" title="Gnome XML Library Reference Manual " link="index.html" version="2" author="" name="libxml">
   <chapters>
     <sub name="Libxml Programming Notes" link="ch01.html">
       <sub name="testOOMlib" link="libxml-testOOMlib.html"/>