Distance from bottom stave to footer

[Nick Payne]

The foot-separation variable that can be used in the \paper block 
doesn't seem to have any effect. It's documented in the 2.13.9 NR as:

foot-separation: Distance between the bottom-most music system and the 
page footer. Default: 4\mm.

but in my test below, putting in different values doesn't change the 
distance between the bottom system and footer at all.

%%===============================================
\version "2.13.9"

date = #(strftime "%d/%m/%Y" (localtime (current-time)))

\paper {
    #(set-paper-size "a4")
    top-margin = 1.5\cm
    bottom-margin = 0.6\cm
    line-width = 18\cm
    foot-separation = 3\cm
    ragged-bottom = ##f
    ragged-last-bottom = ##f
}

\header {
    title = "Title"
    subtitle = "Subtitle"
    composer = "Anon."
    tagline = \markup {
        \fontsize #-3.5
        {
            Engraved on \date using \with-url #"http://lilypond.org/web/";
            { LilyPond \simple #(lilypond-version) (http://lilypond.org/) }
        }
    }
}

notes = \relative c' {
    \repeat unfold 100 { c4 }
}

\score {
    \notes
}
%%===============================================


Nick