new reconfig-recursive target for ports

[Josh Carroll]

> Seems like a rare case where someone would want to re-visit (in this
> manner) options they have already set.  That said, it may come in handy.

Yeah, I figured it can't *hurt* and might come in handy in a few circumstances.

> I think "config-recursive-unconditional" would be a better name as it
> fits better with the "config-recursive" target.  Of course, this is just
> a bikeshed argument so I don't care what it ends up being called.  ;)

I originally named the target config-recursive-force, but the name can
be whatever is most appropriate of course. :)

Josh