2 more bugs with PianoStaff

[Erik Sandberg]

1. The R rests are misplaced (too high in the upper, too low in the lower 
staff).

2. If you comment out \key c\major (which does nothing), you get the following 
warning:

 warning: Change_iterator::process (): Staff = `up':

/tmp/bee/piano.ly:6:21: warning: can't change `Staff' to `down': I'm one 
myself:
    \change Staff=dow
                     n \voiceOne c1 \change Staff=up \oneVoice c R
..and the staff change is not done.

The code:

\version "2.1.34"
\score { \context PianoStaff <<
  \context Staff=up \notes \relative c' {
    \key c\major
    \change Staff=down \voiceOne c1 \change Staff=up \oneVoice c R
  }
  \context Staff=down \notes \relative c'' {
    \voiceTwo c1 \oneVoice R c
  }
>>
\paper{}
}


erik