Fixes all black bars in NR (issue 6345088)

[PhilEHolmes]

Reviewers: Graham Percival, Trevor Daniels, J_lowe,

Message:
Lots of changes here.  The NR still builds successfully following them
all, so I'm fairly confident, but please review if you have time.

Description:
Just a few changed files.  A number of these are in /snippets and I have
updated the LSR to match them already - these are just to illustrate the
changes work.  These changes get rid of all instances of 'overfull hbox'
in the texi2pdf logfile and therefore of all the black sidebars caused
by this.  In a few places I've been forced to use new lines and fiddle
image widths - the latter because of issue 766.

Please review this at http://codereview.appspot.com/6345088/

Affected files:
  M Documentation/included/chord-names-jazz.ly
  M Documentation/included/display-predefined-fretboards.ly
  M Documentation/notation/ancient.itely
  M Documentation/notation/changing-defaults.itely
  M Documentation/notation/chords.itely
  M Documentation/notation/fretted-strings.itely
  M Documentation/notation/input.itely
  M Documentation/notation/notation-appendices.itely
  M Documentation/notation/pitches.itely
  M Documentation/notation/repeats.itely
  M Documentation/notation/simultaneous.itely
  M Documentation/notation/spacing.itely
  M Documentation/notation/staff.itely
  M Documentation/notation/wind.itely
  M Documentation/notation/world.itely
  M Documentation/snippets/ancient-headword.ly
  M Documentation/snippets/changing-the-breath-mark-symbol.ly
  M Documentation/snippets/chant-or-psalms-notation.ly
  M Documentation/snippets/chords-headword.ly
  M Documentation/snippets/editorial-headword.ly
  M Documentation/snippets/expressive-headword.ly
  M Documentation/snippets/figured-bass-headword.ly
  M Documentation/snippets/fretted-headword.ly
  M  
Documentation/snippets/making-some-staff-lines-thicker-than-the-others.ly
  M Documentation/snippets/new/chant-or-psalms-notation.ly
  M Documentation/snippets/new/chords-headword.ly
  M Documentation/snippets/new/fretted-headword.ly
  M Documentation/snippets/new/staff-headword.ly
  M Documentation/snippets/simultaneous-headword.ly
  M Documentation/snippets/staff-headword.ly