space between \header{arranger,opus}

[Graham Percival]

Since bookTitleMarkup and scoreTitleMarkup are separate "systems", the
\paper{betweensystempadding,raggedbottom}  variables affect them.  I can
live with betweensystempadding, but raggedlastbottom (on a small score) 
can
produce some really weird spacing in the title.

I can get all the headers as the same "system" by doing the following, 
but
the arranger+opus headers are still quite close (but not affected by
the paper variables).  I tried adding a
  \override #'(baseline-skip . 3.5)
to the definition of scoreTitleMarkup, but it doesn't seem to change 
anything.
What needs to change in   ly/titling-init.ly  ?


\header{
title="title"
composer="composer"
arranger="arranger"
opus="opus"
}
\paper{
  bookTitleMarkup={}
  printallheaders=##t
}
\book{\score{{
c'4
}}}