Doc build fails on OS X due to issue with xsltproc

[ghost]

The following occurs on stable/v1.6.0, cbd640d.
The standard ./prepare; ./configure --enable-notmuch; make fails on OS X.

Libs installed via homebrew: libxslt, docbook, docbook-xsl.

The error has to do with mutt trying to compile the manual and xsltproc failing out of the box. There may be a way to manually install it, I haven't tried yet.

make[2]: Nothing to be done for `all'.
Making all in doc
xsltproc --nonet -o manual.html ./html.xsl manual.xml
I/O error : Attempt to load network entity http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl
warning: failed to load external entity "http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"
compilation error: file ./html.xsl line 3 element import
xsl:import : unable to load http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl
make[2]: [manual.html] Error 5 (ignored)
LC_ALL=C lynx -dump -nolist -with_backspaces -display_charset=us-ascii manual.html > manual.txt ||
LC_ALL=C w3m -dump manual.html > manual.txt ||
LC_ALL=C elinks -dump -no-numbering -no-references manual.html | sed -e 's,\001, ,g' > manual.txt

I am not sure about the resolution here - at the very least, it would be good to have more precise build instructions for OS X.