NR percussion: Remove advice obsoleted by issue 2240

\parenthesize works fine on single notes.

Conflicts:
	Documentation/notation/percussion.itely
NR percussion: Parenthesis_engraver is available at Score level
Doc-fr: updates NR
 - percussions
 - simultaneous
Doc-es: Typo and nitpick.
Doc-es: Typos.
More consistent performance of breath marks. (issue 3821)

After tied notes, breaths take time only from the last note of the tie, so
e.g. { c4 ~ c8 \breathe } performs as { c4 ~ c16 r }, not { c4 r8 }.
This is consistent with articulations, and with how humans interpret
breaths after ties. This makes it possible to align simultaneous
breaths in multiple parts with different note lengths.

Ignore grace time when calculating the length of the note before a breath —
subsequent grace notes take time from the breath, not the previous note.
Let Chord_name_engraver record lastChord in internal context property

Using a context property instead of an engraver-internal variable
allows for more flexible behavior of identical chord suppression.
Issue 3835: Chord change detection in repeat alternatives

Let chord change detection in repeat alternatives happen in relation
to the chord active at the beginning of the first alternative.
Changes.tely - Document 4 new clefs

Document the 4 new Clefs from commit

476c0adb

Double G, Tenor G, Varpercussion and VarC
Doc: NR: Added @knownissue for midiinstrument

Issue 3823

@knownissue added in 3.5.1 (Creating Midi Files)

Midiinstruments (and other MIDI options) appear twice in the output
Web:Reworded UNIX Download page more strongly not to use distro-based packages

Issue 3829

Reworded 'Generic Packages or ....' section more 'strongly' to  get
users to _not_ use  distribution-specific packages but to use
the generic packages from lilypond.org.

Removed the 'Distribution-specific' Packages section completely.

Added some '32bit/64bit' labels for the generic package download links

Minor grammar and syntax edits
NR: Add verbatim to @lilypond example

NR 1.3.3 - Clef

Added a 'verbatim' to an @knownissue to better
illustrate the example
Doc: make real destructive code innocuous.
Doc: misplaced comments produce wrong HTML output.
Doc: clarify because a «command» is not always a lilypond command.
Revert "Doc: misplaced comments produce wrong HTML output."

This reverts commit b8f58d9897229562d1fb2dc558f8f4309005008d.
Updated snippet/new to remove spurios comments
Run makelsr
Doc-fr : typo in Vocal
Issue 3827: remove the necessity to have a \layout block in a \markup \score ...

It turns out that this is not really fixable in the backend since what
is called "layout" in the markup function definitions does not
actually correspond to \layout but rather to \paper.  Very funny.

So this is solved in the parser itself when reading a \score or
\score-lines to be used in a markup or markup list by cloning
$defaultlayout as necessary (which simulates \layout {}) whenever the
score is without an output definition.