Mention HTMLTidy is required in the INSTALL file (Gerard Beekmans)

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@3809 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

INSTALL

@@ -23,6 +23,12 @@ If all you want to do is convert XML to HTML perform the following:
 * DocBook XSL Stylesheets 
   - http://www.linuxfromscratch.org/blfs/view/cvs/pst/docbook-xsl.html
 
+* HTMLTidy
+  - http://tidy.sourceforge.net/
+
+  Installation of HTMLTidy is a simple `./configure --prefix=/usr && \
+  make && make install`
+
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 If you want to be able to convert the book into PDF as well, then you will need
 the FOP package.  This takes an XSL-FO file (created with libxslt which you