Cyclic redundancies with manual beaming

[Neil Puttock]

Hi guys,

This perfectly innocent looking snippet spits forth several errors
with current master:

\version "2.15.11"

\relative c' {
  s2. c8[ c
  c8 c]
}

/tmp/tmpJ8GqW5/document.ly:4:8: programming error: cyclic dependency:
calculation-in-progress encountered for #'quantized-positions (Beam)
  s2. c8
        [ c
/tmp/tmpJ8GqW5/document.ly:4:8: continuing, cross fingers

  s2. c8
        [ c
/tmp/tmpJ8GqW5/document.ly:4:8: programming error: cyclic dependency:
calculation-in-progress encountered for #'quantized-positions (Beam)
  s2. c8
        [ c
/tmp/tmpJ8GqW5/document.ly:4:8: continuing, cross fingers

  s2. c8
        [ c
/tmp/tmpJ8GqW5/document.ly:4:8: programming error: cyclic dependency:
calculation-in-progress encountered for #'quantized-positions (Beam)
  s2. c8
        [ c
/tmp/tmpJ8GqW5/document.ly:4:8: continuing, cross fingers

  s2. c8
        [ c
/tmp/tmpJ8GqW5/document.ly:4:8: programming error: cyclic dependency:
calculation-in-progress encountered for #'quantized-positions (Beam)
  s2. c8
        [ c
/tmp/tmpJ8GqW5/document.ly:4:8: continuing, cross fingers

  s2. c8
        [ c

I'll try to do a bisect later to narrow it down.

Uh oh, just noticed another one with stem Y-extent too (no manual beam
required here):

\version "2.15.11"

\relative c' {
  \partial 16
  c32 d
}

/tmp/tmp0lpVUz/document.ly:3:2: programming error: cyclic dependency:
calculation-in-progress encountered for #'Y-extent (Stem)

  c32 d
/tmp/tmp0lpVUz/document.ly:3:2: continuing, cross fingers


  c32 d
/tmp/tmp0lpVUz/document.ly:3:2: programming error: cyclic dependency:
calculation-in-progress encountered for #'quantized-positions (Beam)

  c32 d
/tmp/tmp0lpVUz/document.ly:3:2: continuing, cross fingers


  c32 d

Cheers,
Neil