build-sys: make lxml required when generating indices Since the manpage indices generated without lxml would be missing some parts, it doesn't make sense to keep lxml optional anymore.

man: use xinclude to de-deduplicate common text I only tested with python-lxml. I'm not sure if xml.etree should be deprecated.

build-sys: move python helpers to tools directory Note that make-man-rules.py is missing in EXTRA_DIST=, this patch fixes this mistake too.