just add "knob" as a core object
Both moonlib/mknob and flatgui/knob (which itself is pasted from footils/knob) use the same iemgui API. So just add moonlib's source to the core and load as an internal object.
That way we can add creator name "knob" and have it "just work" for all cases.
knob and mknob have slightly different appearances-- knob has a thicker border, but that shouldn't make any functional difference.