gnu: gdm: Look for sessions in /run/current-system.

* gnu/packages/gnome.scm (gdm): Fix search paths for system sessions.  Use
  /var as localstatedir.  Set a more sensible default path for user sessions.

gnu: services: Refactor to separate X and startx wrappers.

* gnu/services/xorg.scm (xorg-wrapper): New public function.
(xorg-start-command): Use xorg-wrapper.

gnu: Add AccountsService service to desktop services.

* doc/guix.texi (Desktop Services): Add accountsservice-service.
* gnu/services/desktop.scm (%accountsservice-activation):
(accountsservice-service-type): New public variables.
(%desktop-services): Add accountsservice-service.

gnu: accountsservice: Properly reference shadow.

* gnu/packages/freedesktop.scm (accountsservice): Fix references to binaries
  provided by the shadow package.

gnu: parallel: Update to 20170822.

* gnu/packages/parallel.scm (parallel): Update to 20170822.

gnu: yoshimi: Update to 1.5.3.

* gnu/packages/music.scm (yoshimi): Update to 1.5.3.

gnu: zynaddsubfx: Update to 3.0.2.

* gnu/packages/music.scm (zynaddsubfx): Update to 3.0.2.

gnu: guile-xcb: Update source URL.

* gnu/packages/guile-wm.scm (guile-xcb)[source]: Use archived tarball URL.

graft: Correctly replace references near the end of the scan buffer.

Fixes <http://bugs.gnu.org/28212>.
Reported by Leo Famulari <leo@famulari.name>.

* guix/build/graft.scm (replace-store-references): When I >= END, check
whether WRITTEN > END and call 'get-bytevector-n!' when it is.
* tests/grafts.scm (buffer-size): New variable.
("replace-store-references, <http://bugs.gnu.org/28212>"): New test.

Revert "graph: Provide access to the package record in the emit functions."

This reverts commit 5d7e8543659874682b618bba799ba7cd6ffce554, which
broke 'tests/graph.scm' and broke node types not related to <package>
objects, such as '%reference-node-type'.

gnu: font-mathjax: Move to javascript.scm.

This avoids cross-module top-level references.

* gnu/packages/fonts.scm (font-mathjax): Move to...
* gnu/packages/javascript.scm (font-mathjax): ... here.  New variable.

gnu: font-go: Remove reference to 'go-1.4'.

This avoids circular references at the top level.

* gnu/packages/fonts.scm (font-go)[license]: Remove reference to
GO-1.4.

gnu: Add honcho.

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

Signed-off-by: Marius Bakke <mbakke@fastmail.com>

gnu: maim: Update to 5.4.68.

* gnu/packages/xdisorg.scm (maim): Update to 5.4.68.

gnu: slop: Update to 7.3.49.

* gnu/packages/xdisorg.scm (slop): Update to 7.3.49.

gnu: guile-wm: Update source URL.

* gnu/packages/guile-wm.scm (guile-wm)[source]: Use archived URL.

gnu: libreoffice: Fix icons, enable liblangtag.

* gnu/packages/libreoffice.scm (libreoffice) [inputs]: Add liblangtag.
  [arguments]: Correct icon names in .desktop files; copy desktop files &
  icons for libreoffice-math and libreoffice-startcenter; enable parallel
  build; enable liblangtag.

gnu: dovecot: Update to 2.2.32.

* gnu/packages/mail.scm (dovecot): Update to 2.2.32.

gnu: lollypop: Use pseudo meson build system.

* gnu/packages/gnome.scm (lollypop)[arguments]: Disable tests. Delete
configure phase, replace build and install phase with custom phases.
[native-inputs]: Add ninja.
[propagated-inputs]: Move gst-plugins-base ...
[inputs]: ... to here. Add meson.

gnu: libksysguard: Enable more tests (not all working yet).

* gnu/packages/kde.scm (libksysguard)[arguments]
  <#:phases>'check-setup': Set QT_QPA_PLATFORM=offscreen.
  <#:phases>'check': Enable all tests except of the failing one.