Setting rehearsal mark value in non=default context

[Timothy Lanfear]

An integer argument to \mark is not respected if the mark engraver is 
moved from the Score context. The example creates rehearsal marks "A", 
"B", not "A", "C".

\version "2.19.49"

\layout {
  \context {
    \Score
    \remove "Mark_engraver"
    \remove "Staff_collecting_engraver"
  }
  \context {
    \Staff
    \consists "Mark_engraver"
    \consists "Staff_collecting_engraver"
  }
}

<<
  \new Staff { R1 R1 R1 }
  \new Staff { R1 \mark \default R1 \mark #3 R1 }
>>

--

Timothy Lanfear, Bristol, UK.