refresh: Discard PyPI updater when Guile-JSON is missing.

Reported by Sleep_Walker and Mathieu Lirzin <mthl@gnu.org>.

* guix/scripts/refresh.scm (maybe-updater, list-updaters): New macros.
  (%updaters): Use 'list-updaters' instead of 'list'.  Make
  %PYPI-UPDATER conditional.

gnu: Add wcalc.

* gnu/packages/maths.scm (wcalc): New variable.

gnu: octave: Upgrade to 4.0.0.

* gnu/packages/maths.scm (octave): Update to 4.0.0.

gnu: glpk: Update to 4.57.

* gnu/packages/maths.scm (glpk): Update to 4.57.

gnu: evince: Update to 3.18.1.

* gnu/packages/gnome.scm (evince): Update to 3.18.1.

gnu: Add gjs.

* gnu/packages/gnome.scm (gjs): New variable.

gnu: Add mozjs-24 (Mozilla SpiderMonkey 24).

* gnu/packages/gnuzilla.scm (mozjs-24): New variable.

gnu: Add gnome-session.

* gnu/packages/gnome.scm (gnome-session): New variable.

gnu: gnome-themes-standard: Update to 3.18.0.

* gnu/packages/gnome.scm (gnome-themes-standard): Update to 3.18.0.

gnu: gnome-desktop: Update to 3.18.1.

* gnu/packages/gnome.scm (gnome-desktop): Update to 3.18.1.
  Move gsettings-desktop-schemas and gtk+ to 'propagated-inputs'.
  [native-inputs]: Add gobject-introspection.

install: Run GPM.

Suggested by Adam Pribyl <pribyl@lowlevel.cz>
at <https://lists.gnu.org/archive/html/guix-devel/2015-11/msg00133.html>.

* gnu/system/install.scm (installation-services): Add call to
  'gpm-service'.
* doc/guix.texi (System Installation): Mention GPM.

services: Add 'gpm-service'.

* gnu/services/base.scm (<gpm-configuration>): New record type.
  (gpm-dmd-service): New procedure.
  (gpm-service-type): New variable.
  (gpm-service): New procedure.
* doc/guix.texi (Base Services): Document it.

gnu: brasero: Use 'glib-or-gtk-build-system'.

Fixes <http://bugs.gnu.org/21842>.
Suggested by Andy Wingo <wingo@pobox.com>.

* gnu/packages/gnome.scm (brasero)[build-system]: Switch to
  GLIB-OR-GTK-BUILD-SYSTEM.

gnu: icecat: Add several security fixes.

* gnu/packages/patches/icecat-CVE-2015-4513-pt01.patch,
  gnu/packages/patches/icecat-CVE-2015-4513-pt02.patch,
  gnu/packages/patches/icecat-CVE-2015-4513-pt03.patch,
  gnu/packages/patches/icecat-CVE-2015-4513-pt04.patch,
  gnu/packages/patches/icecat-CVE-2015-4513-pt05.patch,
  gnu/packages/patches/icecat-CVE-2015-4513-pt06.patch,
  gnu/packages/patches/icecat-CVE-2015-4513-pt07.patch,
  gnu/packages/patches/icecat-CVE-2015-4513-pt08.patch,
  gnu/packages/patches/icecat-CVE-2015-4513-pt09.patch,
  gnu/packages/patches/icecat-CVE-2015-4513-pt10.patch,
  gnu/packages/patches/icecat-CVE-2015-4513-pt11.patch,
  gnu/packages/patches/icecat-CVE-2015-7188.patch,
  gnu/packages/patches/icecat-CVE-2015-7189.patch,
  gnu/packages/patches/icecat-CVE-2015-7193.patch,
  gnu/packages/patches/icecat-CVE-2015-7194.patch,
  gnu/packages/patches/icecat-CVE-2015-7196.patch,
  gnu/packages/patches/icecat-CVE-2015-7197.patch,
  gnu/packages/patches/icecat-CVE-2015-7198.patch,
  gnu/packages/patches/icecat-CVE-2015-7199.patch: New files.
* gnu-system.am (dist_patch_DATA): Add them.
* gnu/packages/gnuzilla.scm (icecat)[source]: Add patches.

gnu: nss: Update to 3.20.1.

* gnu/packages/gnuzilla.scm (nss): Update to 3.20.1.
  [source]: Switch to https URI.

gnu: nspr: Update to 4.10.10.

* gnu/packages/gnuzilla.scm (nspr): Update to 4.10.10.

gnu: Add GPM.

* gnu/packages/linux.scm (gpm): New variable.

doc: Make the ifconfig command more visible.

Suggested by Adam Pribyl <pribyl@lowlevel.cz>.

* doc/guix.texi (System Installation): Move the 'ifconfig' command to an
  @example.

gnu: Add guile-gnunet.

* gnu/packages/gnunet.scm (guile-gnunet): New variable.

gnu: bless: Correct indentation and home-page.

* gnu/packages/bioinformatics.scm (bless): Fix indentation.
  [home-page]: Replace broken URL.