#5138 New voice with cluster changes horizontal spacing

[Colin Campbell]

Reported by Klaus Blum:
I`ve run into the following issue:
When I temporaryly create a new voice that contains clusters, the horizontal
spacing is changed.
Removing the "\new Voice" command makes the problem disappear.

\new Staff {
  c'4 d' e' f' g' f' e' d'
  <<
    {c'4 d' e' f' g' f' e' d'}
    \new Voice
    \makeClusters {c'4 d' e' f' g' f' e' d'}
  >>
  c'4 d' e' f' g' f' e' d'
}

For pictures see:
http://lilypond.1069038.n5.nabble.com/new-voice-with-cluster-changes-horizontal-spacing-td203189.html
I've tested this with LP 2.18.2, 2.19.37 and 2.19.58 and got the same result
with all those versions.