Doc-fr: updates rhythms, running and texidocs
Doc-it: add Notation Reference 1.2

Still waiting for proofreading, I'll add changes later.
Doc-it: update
Doc-de: Typo
Issue 3151: NR 3.4.1: \layout block wrongly placed in a \book block causes error
Update essay to correct display of articulations
PO: update template.
Release: update news.
Release: bump version.
Doc: add some missing italian translations in Music Glossary
Issue 3303: Add some more documentation for \defaultchild
doc: explain how to add lyrics to polyphonic sections (issue 3236)
Doc: use @dots{} rather than "..."
Add warning about using \relative with tagged music (3253)

 - add warning as a known issue
 - remove earlier ignored known issue
Revert "Break slurs between alternative endings in repeats; issue 1698."

This reverts commit 88d306d9c5666b5ade4a136df29cca19c5ff5ed7.

Conflicts:

	input/regression/repeat-slur.ly
Doc: Error message: unexpected \new (3285)

  Explain reason for the message and what should be
  done to avoid it.
Adds arpeggio to conditional item grob array.

The actual function of conditional elements was not correctly reflected
in the comment above Separation_item::boxes.  This comment led one to believe
that conditional elements were only used when notes with accidentals
had ties coming to them.  This is not true.  Conditional elements are always
used for right columns when there is something to the left (see
Spacing_interface::skylines).  They are omitted _only_ when they are
accidentals with ties coming to them.

So why do we want an arpeggio to be a conditional element?  There is
nothing conditional about it (it will always be printed, unlike accidentals
with ties going to them).  It is because conditional elements have the
double duty of being conditional (i.e. accidentals) AND being factored
into springs in note spacing (see the long comment in
Note_spacing::get_spacing) in the calculation of a spring's ideal distance.
Other elements to the left of a note column, like scripts and fingerings,
are only factored into the minimum distance. We want arpeggios to factor
into the ideal distance because otherwise they will be too close to
left note-columns in tight spacing situations.

Lastly, there was no reason in the code base to keep a pointer to the
arpeggio in the note column, so it is removed here.
Time signature before repeat bars at beginning of line; issue 828
skyline.cc: No zero-width empty buildings between buildings; issue 3311
Add additional options grdp to scripts/auxiliar/make-regtest-pngs.sh

This is for checking bitmap production at different resolution, the
output from using poppler and libcairo on LilyPond's PDF, and the
output for typical print bitmaps generated from LilyPond's PDF.