gnu: udisks: Enforce non-reference of the "doc" output.

* gnu/packages/freedesktop.scm (udisks)[arguments]: Add
  #:disallowed-references.

system: Make sure fonts are searched for in the system profile.

This fixes a bug whereby fonts in /run/current-system/profile would be
invisible to Fontconfig.

* gnu/packages/fontutils.scm (fontconfig): Add comment about system
profile not being searched.
* gnu/system/shadow.scm (default-skeletons)[fonts.conf-content,
fonts.conf]: New variable.
Add FONTS.CONF to the skeletons.

gnu: gnome: Add dependency on font-abattis-cantarell.

* gnu/packages/gnome.scm (gnome)[propagated-inputs]: Add
FONT-CANTARELL.

system: Allow account skeletons to be directories.

* gnu/system/shadow.scm (skeleton-directory): Use 'copy-recursively'
instead of 'copy-file'.
* gnu/build/activation.scm (copy-account-skeletons): Likewise.

gnu: Add font-abattis-cantarell.

* gnu/packages/fonts.scm (font-cantarell): New variable.

gnu: fontforge: Make builds bit-reproducible.

* gnu/packages/fontutils.scm (fontforge)[source](snippet, modules): New
fields.

gnu: fontforge: Update to 20150824.

* gnu/packages/fontutils.scm (fontforge): Update to 20150824.
[inputs]: Add libltdl, libxft, python.
[native-inputs]: New field.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

gnu: kodi: Remove @acronym from description.

This works around <http://bugs.gnu.org/21772>.

* gnu/packages/kodi.scm (crossguid): Remove @acronym.

gnu: r-dnacopy: Fix home page URL.

* gnu/packages/bioinformatics.scm (r-dnacopy)[home-page]: Add missing
URI scheme.

gnu: gnome: Disable hardware acceleration check via 'gnome.desktop'.

* gnu/packages/gnome.scm (gnome-session)[arguments]: Add
'disable-hardware-acceleration-check' phase.

services: xorg: Accept session commands with arguments.

Before that, a session command with several items, such as
'gnome-session --disable-acceleration-check', would trigger the fallback
session.

* gnu/services/xorg.scm (xinitrc)[builder]: Accept command lines with
more than one arguments.

gnu: gnome-session: Make sure 'gsettings' is found.

* gnu/packages/gnome.scm (gnome-session)[arguments]: Add
'wrap-gnome-session' phase.

gnu: Add beets.

* gnu/packages/music.scm (beets): New variable.

gnu: Add python-rarfile.

* gnu/packages/python.scm (python-rarfile, python2-rarfile): New
variables.
* gnu/packages/patches/python-rarfile-fix-tests.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.

gnu: Add python2-unicodecsv.

* gnu/packages/python.scm (python2-unicodecsv): New variable.

gnu: Add python-jellyfish.

* gnu/packages/python.scm (python-jellyfish, python2-jellyfish): New variables.

gnu: Add python-mpd2.

* gnu/packages/mpd.scm (python-mpd2, python2-mpd2): New variables.

gnu: Add python2-pathlib.

* gnu/packages/python.scm (python-pathlib, python2-pathlib): New variables.

gnu: Add python-responses.

* gnu/packages/python.scm (python-responses, python2-responses): New variables.

gnu: Add python-cookies.

* gnu/packages/python.scm (python-cookies, python2-cookies): New variable.