late instrumentSwitch in MIDI output

[Dan Eble]

In this example, the MIDI output does not switch instruments properly at the
beginning of measure five.  I'm sorry this is not a very simple example, but
small alterations make the problem disappear.

(Yes, I realize that this is an abuse of instrumentCueName, but I see no reason
why the MIDI output should disagree with the visual output.)

I am using 2.12.0 built for PowerPC on Mac OS X 10.5.6.

Thanks,
-- 
Dan

\version "2.11.65"

\include "english.ly"

\addInstrumentDefinition #"cello.pizz"
  #'((instrumentCueName . "pizz.")
     (midiInstrument . "pizzicato strings"))

\addInstrumentDefinition #"cello.arco"
  #'((instrumentCueName . "arco")
     (midiInstrument . "cello"))

arco = \markup { \italic arco }
pizz = \markup { \italic pizz. }

cello = \relative af,
{
  \time 4/4
  \tempo 4 = 120

  af8 r r4 f8 r r4 |
  bf4 c8. df16 ef4~ ef8. f16 |
  gf4 f bf,~ \times 2/3 { bf8 c df } |
  ef4 r ef, r |
  \instrumentSwitch "cello.pizz" af^\pizz r af r |

  R1 |
  \instrumentSwitch "cello.arco" ef4^\arco e f gf |
  g ef af2 |
  af8 r \instrumentSwitch "cello.pizz" af^\pizz r af r af r |

  \bar "|."
}

\score
{
  \context Staff
  {
    \set Staff.instrumentName = "Cello"
    \set Staff.midiInstrument = "cello"
    \clef "bass"
    \cello
  }

  \layout { }

  \midi { }
}