bug#27833: 25.2; Add support for manpath command to woman.el

[Eli Zaretskii <eliz@gnu.org>]

> From: Reuben Thomas <rrt@sc3d.org>
> Date: Tue, 25 Jul 2017 23:41:03 +0100
> 
> The attached patch against git master adds support for the man-db
> manpath command to woman.el.
> 
> For now, this can actually be better than using man, as man -k/apropos
> does not currently support man directories lacking a database or whatis
> file, which is typical for directories derived from PATH.

Could you please provide a rationale for this addition?

It sounds strange to me to enhance woman.el, whose main purpose is to
work without ("wo") 'man', including on systems where 'man' is not
easily available, by making it run 'manpath'.  If something is wrong
with woman-manpath's built-in database, why cannot we extend it by
adding potential candidates to those already existing there?

On top of that, I think we semi-deprecated woman.el because AFAIR it
cannot support newer roff features which are abundant in recent man
pages.  So I wonder what kind of use case do you have that on the one
hand needs woman.el, and OTOH finds its manpath emulation lacking.