Docs and the :manpage: tag

[Nicola Nye]

G'day,

Nic B and Jeroen, I think this is mostly something you'll have some
thoughts about...

Currently the rst docs make use of a :manpage: tag. This does little
more than change the formatting of the affected text.

For the html docs, it makes far more sense for it to convert it to the
link for the relevant man page. (while not affecting any other output
format generation such as the actual man pages)

Anyone have any objections before I just go ahead and do it?

   Nicola