Ugly artifacts in chordname staff

[eluze]

hi Laszlo

i think the nesting is the cause of this uglyness (and 2.12.3 ws more  
tolerant against this).

rearranging could look like this:

\score {
  <<
    \context ChordNames = chordsU \chordsU
    \context Staff = cStaffU <<
      \tempo 4 = 72
      \context Voice = cStaffU \staffU
      \context Lyrics = cStaffU { \set stanza = "1." }
      \context Lyrics = cStaffU \lyricsto cStaffU \textU
    >>
  >>
  \layout {
    indent = 0\cm
    \context { \StaffGroup
      \remove "System_start_delimiter_engraver"
    }
    \context { \Score
      \override TimeSignature #'stencil = ##f
      \remove Metronome_mark_engraver
      \remove Bar_number_engraver
    }
  }
}

rgds
Eluze