MIDI ignores dynamics parallel to notes

[Richard Sabey]

Lilypond's MIDI output sometimes fails to account for dynamic indications if the
code specifies them in parallel with the music rather than directly attached to
notes.

In the example, the notes sound fairly loud to me.

Related to issue 1646?
%%%%%%%%%%%%%%%%%%%%%%
\version "2.13.61"

\score
{
        <<
                \new Staff \with { midiInstrument = #"contrabass"}
                        <<
                                { c2  f  }
                                { s1\pppp }
                        >>
        >>
        \midi
        {
                \context
                {       \Staff
                        \remove "Staff_performer"
                }
                \context
                {       \Voice
                        \consists "Staff_performer"
                }
        }
} % score
%%%%%%%%%%%%%%%%%%%%%%