Incorrect stemming

[J. David Blackstone]

Tested under version 2.5.29 on Windows.

Using the new \aikenHeads feature, entering an identical note for two 
voiceparts in polyphony results in incorrect stemming and an incorrect notehead 
unless the note is sol (round note).  Example:

\version "2.5.29"
\score
{
<<
 \new Staff
 {
  \clef treble
  \key c \major
  
  <<
  \aikenHeads
   {
     << { g'4 c''4 } \\
        { g'4 c''4 } >>
   } \\

  >>
 }
>>
\layout { }

The first note is correct; the second should consist of only a do (triangle) 
and the downward stem should be attached to the lower extremity of its left 
side.

This probably occurs in \sacredHarpHeads, too, but I think double-stemming a 
note is not as common in that notation.

jdb