Rest collision bug

[Mats Bengtsson]

If you don't explicitly specify the "stem direction" of 
a voice of rests colliding with some other music, the 
rest collision handling should determine the direction
to move based on the other music voice. This doesn't
work now as examplified in this example:

\score{\notes\relative c''
  \context Staff <
    \time 2/4
    \context Voice=upper {
      %\voiceOne % Uncommenting this line gives the desired result
      r4 r8 e }
    \context Voice=lower {\voiceTwo
      b8 a  g s }
   >
}

The problem occurs (at least) in Lilypond 1.5.51.

   /Mats