Merge branch 'master' into lilypond/translation

* master:
  Fix use of relative in docs and restore UTF-8 strings
  compile fix (apparently)
  Formatting nits.
  Remove stray letter.
  New dynamics engravers
  Small formatting cleanups.
  Add Drul_array<>::set() method.
  Add ly:prob-[im]mutable-properties Scheme bindings.
  Restore Tie direction default
  Add NEWS entry for arpeggio.
  Fix #455.
  Fix #521.
  Bump version.
  Make fast_substitute_grob_array() protected.
  Fix #434, #440
  Add Skyline_pair::print[_point](), add some minor cleanups.
  Move Skyline_pair and Paper_system bindings into their own files.
  code layout nits.
  Fix #578.

diff --cc Documentation/es/user/simultaneous.itely
Simple merge