I do see some use for disabling the header, but changing it from the
default seems a bit of a niche feature for an http daemon that is
intentionally quite barebones.

(The original author would probably tell you to strip it in relayd..
https://github.com/reyk/httpd/issues/39#issuecomment-103416671)

> > +.It Oo Ic no Oc Ic disablebanner
> > +Suppresses the server software name in HTTP headers and error documents
> > +for the current
> > +.Ic server.
> > +The
> > +.Ic no
> > +keyword can be used to override the global setting.

This syntax is awkward. If this _is_ added, it would be better as
'banner "foo"', 'no banner', and 'banner' (the latter for the case
where you set 'no banner' globally and want to override to use
the default string for a particular server).