workaround for \partcombine limitation, how to add to docs?

[Mark Polesky]

In NR 1.5.2 Multiple voices - Automatic part combining, this
appears in the Known issues:

"All \partcombine… functions can only accept two voices and
are not designed to work with lyrics; such that when one of
the voices is explicitly named in order to attach lyrics to
it, the partcombiner will stop working."

http://lilypond.org/doc/v2.17/Documentation/notation/multiple-voices#Known-issues-and-warnings-82

I have found a workaround, detailed below.  What is the best
way to include this in the docs?

Thanks.
- Mark
______________________


\version "2.17.21"

sopranoNotes = \relative g' {
  g4 fis8( g) a4 g |
  c4 c b2
}
altoNotes = \relative d' {
  d4 d d d |
  c4 d d2
}
words = \lyricmode {
  As with glad -- ness men of old
}

squashRhythmicStaff = \with {
  \remove Time_signature_engraver
  \remove Bar_engraver
  \remove Staff_symbol_engraver
  \override VerticalAxisGroup.default-staff-staff-spacing =
  #'((basic-distance . 0) (padding . -inf.0))
}

squashVoice = \with {
  \remove Breathing_sign_engraver
  \remove Glissando_engraver
  \remove Multi_measure_rest_engraver
  \remove Pitched_trill_engraver
  \remove Repeat_tie_engraver
  \remove Trill_spanner_engraver

  \omit DynamicLineSpanner
  \omit DynamicText
  \omit DynamicTextSpanner
  \omit Hairpin
  \omit ParenthesesItem
  \omit PhrasingSlur
  \omit Script
  \omit Slur
  \omit TextScript
  \omit TextSpanner
  \omit Tie

  \override Stem.length = #0
  \override Beam.positions = #'(1 . 1)

  \hideNotes
}

<<
  \new RhythmicStaff \with { \squashRhythmicStaff } {
    \new Voice = "soprano" \with { \squashVoice } \sopranoNotes
  }
  \new Staff \with { printPartCombineTexts = ##f } {
    \key g \major
    \partcombine \sopranoNotes \altoNotes
  }
  \new Lyrics \lyricsto "soprano" \words
>>