Hi Guix,

here are four patches to add Frescobaldi, a score editor for Lilypond,
and some as yet unpackaged dependencies.

First off: as this depends on Lilypond, and Lilypond uses Ghostscript to
convert Postscript files to PDF, and this feature is broken until we
update fontconfig to 2.11.94, one of the core features of Frescobaldi
(rendering a score with Lilypond) isn’t actually working right now.

AFAIK a patch to update fontconfig was submitted for the core-updates
branch already.

Frescobaldi needs poppler-qt4, a library that is built by poppler when
Qt4 is found at build time.  I created a variant of the poppler package
because I don’t want to add an unnecessary indirect dependency on Qt4
for every package using poppler.

~~ Ricardo