top-spacing-markup incorrect behavior for top-level markup

[Sharon Rosner]

> I'm not top posting.

When using top-spacing-markup and mixing both scores with title markup and 
arbitrary top-level markup, lilypond positions markup at the top of the page in 
an inconsistent manner.

For score title markup, lilypond will consider the top-markup-spacing setting 
as the distance between the top-margin and the _top_ of the markup. For 
top-level markup, lilypond will consider the top-markup-spacing setting as the 
distance between the top-margin and the _baseline_ of the markup.

The following example demonstrates the inconsistent behaviour (notice the 
difference in positioning of the titles on the two pages):

\paper {
  annotate-spacing = ##t
  ragged-bottom = ##t

  top-markup-spacing #'basic-distance = 10
  top-markup-spacing #'minimum-distance = 10
  top-markup-spacing #'padding = 0 % negative padding to ignore skyline
  top-markup-spacing #'stretchability = 0 % fixed position
}

\score {
  \header {
    piece = \markup "1 - Hey"
  }
  R1*3
}

\pageBreak
\markup "2 - Hey"


Thanks
Sharon Rosner