devel: make man-to-mdwn.pl to work with generated manual pages

devel: make man-to-mdwn.pl to work with generated manual pages

The new manual pages converted from rst using sphinx or rst2man
has somewhat different syntax. man-to-mdwn.pl is now adjusted
to produce even better output from this syntax. The changes also
include using utf-8 locale (e.g. for tables and generated hypens)
and and quite a few bugs fixes.
This tool still produces better results than just using the
html pages generated using sphinx / rst2html. For example those
tools don't create inter-page hyperlinks -- and the preformatted
pages written by man-to-mdwn.pl just works well with manual page
content.