binding-offset bug

[Karol Majewski]

Hi,

it seems that binding-offset size scales accordingly to global-staff-size, 
which of course is a bug:

%%%%%%%%%%%%%%%%%%%%%%%%%%%

\version "2.19.10"

#(set-global-staff-size 20)

\paper {
  top-markup-spacing = #'((basic-distance . 0) (minimum-distance . 0) (padding 
. 0) (stretchability . 0))
  two-sided = ##t
  binding-offset = 2\cm
}

\bookpart {
  \header {
    poet = \markup { \abs-fontsize #13 "left" }
    composer = \markup { \abs-fontsize #13 "right" }
  }
  \score {
    \new Staff { d'4 }
  }
}

%%%%%%%%%%%%%%%%%%%%%%%%%%%

Now, change global-staff-size to smaller and you'll notice that inner-margin 
becomes smaller too! However, when binding-offset is disabled, changing 
global-staff-size does not affect inner-margin size.

Best
--Karol