Fix: doc/man: use a single XSL file and match local names

Matching the local name instead of the full name, that is:

   *[local-name() = 'co']

instead of just `co` matches both the non-namespaced element and
the DocBook-namespaced element whether we're using the DocBook 4.5 or
DocBook 5.0 stylesheets.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>