DocBook detection in autoconf is against an old version; patch enclosed
Running ./configure on a stock 7.0.0.20101026 snapshot reports:
checking for DocBook DTD... I/O error : Attempt to load network entity http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd
conftest.xml:5: warning: failed to load external entity "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
]>
^
conftest.xml:6: element book: validity error : No declaration for attribute id of element book
<book id="test">
^
conftest-book.xml:2: parser error : Entity 'ldquo' not defined
<title>A DocBook “Test Document”</title>
^
conftest-book.xml:2: parser error : Entity 'rdquo' not defined
<title>A DocBook “Test Document”</title>
^
conftest-book.xml:11: parser error : chunk is not well balanced
^
conftest.xml:7: parser error : Failure to process entity conftest-book
&conftest-book;
^
conftest.xml:7: parser error : Entity 'conftest-book' not defined
&conftest-book;
^
failed
configure: WARNING: cannot find a DTD for DocBook XML V4.2, you will not be able to validate your documentation
configure: WARNING: check your XML_CATALOG_FILES environment variable and/or /etc/xml/catalog
checking for xsltproc... /usr/local/bin/xsltproc
checking for DocBook XSL stylesheet... no
configure: WARNING: cannot find DocBook XSL stylesheets, you will not be able to build the documentation
But this is erroneous because I have laboriously installed DocBook's XSL many times. I traced the problem to the fact that autoconf was checking specifically for version 4.2, and I have installed version 4.5, which is the latest as of this writing. Bumping the version numbers in aclocal.m4 and running autoreconf fixed the problem. Patch attached.