Tighten DocBook requirements in README
README contains:
Requirements
============
The DocBook XML DTD.
http://www.oasis-open.org/docbook/
The DocBook XSL Stylesheets.
http://docbook.sourceforge.net/projects/xsl/
configure.ac contains:
dnl check for DocBook DTD and stylesheets in the local catalog.
JH_CHECK_XML_CATALOG([-//OASIS//DTD DocBook XML V4.3//EN], [DocBook XML DTD V4.3])
JH_CHECK_XML_CATALOG([http://docbook.sourceforge.net/release/xsl/current/html/chunk.xsl], [DocBook XSL Stylesheets])
The latest DocBook version today is 5.0.1.
Update README to state, whether at least 4.3, exact 4.3, or anything 4.3…4.5 is required