#5514 Documentation: elaborate NR `custom percussion’ section

[Valentin Villenave]

Documentation: elaborate NR `custom percussion’ section

This patch adds a substantial amount of information to
NR 2.5.1.6 "Custom percussion staves", with examples
inspired by LSR #1033 and index entries for previously
undocumented variables and properties.

Accordingly, that snippet is no longer relevant in
the snippets list (it has been untagged as `docs’
in the LSR and should therefore not be brought back
by next makelsr update).

http://codereview.appspot.com/550650043

[Anonymous]

Passes make, make check and a full make doc.

[Anonymous]

Patch on countdown for April 30th - note there are some minor edits suggested on Rietveld.

[Anonymous]

Patch counted down - there are some nits from Werner on Rietveld - but these won't stop the countdown.

[Anonymous]

Patch counted down - there are some nits from Werner on Rietveld - but these won't stop the countdown.

[Anonymous]

Valentin, this has been counted down so you can push to staging (there are some nits from Werner on Rietveld - but these won't stop the countdown).

[Valentin Villenave]

Thanks for reminding me, James.
Pushed as https://git.savannah.gnu.org/cgit/lilypond.git/commit/?id=bc46cc1fef7eecd0a64ac60223d40e98d79c9958; please verify!