Linebreak difference between 2.10.33 and 2.12.2

[Andreas Scherer]

The following code produces a single line with Lilypond 2.10.33, but two lines 
with Lilypond 2.12.2. Why? (convert-ly only changed the \version number.)

Cheers,
Andreas

<pavane.ly>
%
% 2006-09-01, Was lernen wir heute?
%
% Unvollständiger, einleitender Takt: \partial 4*3
% Systemwechsel (hatten wir schon mehrfach): \change Staff = {upper,lower}
% Größenänderungen mit \tiny, \small und \normalsize
% Positionierung: \set suggestAccidentals
% Verkürzte Systeme: indent, line-width
%
\version "2.12.0"

\header {
        title = "Pavane Op. 50"
        composer = "Gabriel Fauré (1845─1924)"
        enteredby = "Andreas Scherer"
}

global = { \time 4/4 \key fis \minor }

upstaff = \change Staff = upper
lowstaff = \change Staff = lower

\score {
         \new PianoStaff <<
                \context Staff = upper <<
                  \global \relative c'' {
                        << {e8(d)c r r2 |
                        s1 | s 1 | s1 | } \\
                        { r4 \slurUp c,2(d4 |
                        \stemUp e f d e |
                        c2 bes4 d |
                        cis!8) } >>
                } >>
                \context Staff = lower <<
                  \global \clef bass \relative c' {
                        << { r4 r8 bes a16 g f e f8 e |
                        d c d e f \upstaff \stemDown g a bes |
                        a g \lowstaff \stemUp f e f e d16 e f
                                \upstaff \stemDown g |
                        { \tiny a8-. cis-. e-. cis-.
                                \lowstaff \stemUp a-. cis-. e-. cis-. } } \\
                        { b,1~ |
                        b4 a2(g4) |
                        bes(a) d(bes) |
                        a1 | } >> }
                >>
        >> 

        \midi {
          \context {
            \Score
            tempoWholesPerMinute = #(ly:make-moment 108 4)
          }
        }

        \layout{
           indent = 0\mm
        }
}
</pavane.ly>