The rst2man tool is provided by python docutils, and as the name
suggests, it converts RST documents into man pages.

The intention is that our current POD docs will be converted to
RST format, allowing one more use of Perl to be eliminated from
libvirt.

The manual pages will now all be kept in the docs/manpages/ directory,
which enables us to include the man pages in the published website.
This is good for people searching for libvirt man pages online as it
makes it more likely google will send them to the libvirt.org instead
of some random third party man page site with outdated content.
Reviewed-by: NCole Robinson <crobinso@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>