gnu: Add qrencode.

* gnu/packages/aidc.scm (qrencode): New variable.

gnu: Consolidate libjpeg, libpng, and libtiff into one module.

* gnu/packages/image.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add image.scm and remove libjpeg.scm,
  libpng.scm, and libtiff.scm.
* gnu/packages/libjpeg.scm, gnu/packages/libpng.scm, gnu/packages/libtiff.scm:
  Delete files.
* gnu/packages/emacs.scm gnu/packages/games.scm, gnu/packages/gd.scm,
  gnu/packages/geeqie.scm, gnu/packages/ghostscript.scm,
  gnu/packages/gimp.scm, gnu/packages/gnome.scm, gnu/packages/gnunet.scm,
  gnu/packages/gnustep.scm, gnu/packages/gnuzilla.scm,
  gnu/packages/graphviz.scm, gnu/packages/gtk.scm,
  gnu/packages/imagemagick.scm, gnu/packages/inkscape.scm,
  gnu/packages/netpbm.scm, gnu/packages/pdf.scm, gnu/packages/plotutils.scm,
  gnu/packages/qemu.scm, gnu/packages/qt.scm, gnu/packages/scheme.scm,
  gnu/packages/sdl.scm, gnu/packages/slim.scm, gnu/packages/tcl.scm,
  gnu/packages/texlive.scm, gnu/packages/video.scm, gnu/packages/xiph.scm,
  gnu/packages/xorg.scm: Use (gnu packages image) module.

gnu: Enable libvpx support in ffmpeg.

* gnu/packages/video.scm (ffmpeg): Add libvpx input.

system: Adjust the set of fields with default values.

* gnu/system.scm (<operating-system>)[file-systems]: Remove default.
  [locale]: Add default value.

guix system: Add 'reconfigure' action.

* guix/scripts/system.scm (%system-profile): New variable.
  (switch-to-system, previous-grub-entries): New procedures.
  (unless-file-not-found): New macro.
  (show-help): Add 'reconfigure'.
  (guix-system): Handle it.
* gnu/system.scm: Export 'operating-system-activation-script'.
* doc/guix.texi (Invoking guix system): Document it.

activation: Preserve /etc/groups upon reboots.

This is a followup to e2fcc23.  The /etc/group file would be cleared
when booting.

* guix/build/activation.scm (activate-users+groups)[touch]: Rewrite so
  it does not wipe out FILE's contents.

guix {system,offload}: Improve reporting of syntax errors.

* guix/scripts/system.scm (read-operating-system) <catch handler>: Add
  case for 'syntax-error'.  Correct message for default case.
* guix/scripts/offload.scm (build-machines) <catch handler>: Add case
  for 'syntax-error'.
* tests/guix-system.sh: New file.
* Makefile.am (SH_TESTS): Add it.

gnu: Add libsodium.

* gnu-system.am (GNU_SYSTEM_MODULES): Add crypto.scm.
* gnu/packages/crypto.scm: New file.

gnu: Add guile-opengl.

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

gnu: Add libvpx.

* gnu/packages/video.scm (libvpx): New variable.

gnu: Add new package barcode

* gnu/packages/aidc.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.

system: Support the addition of old entries in the GRUB menu.

* gnu/system.scm (operating-system-grub.cfg): Add 'old-entries'
  parameter.  Pass it to 'grub-configuration-file'.
* gnu/system/grub.scm (grub-configuration-file): Add #:old-entries
  parameter.  Honor it.

system: Store boot parameters in the system derivation.

* gnu/system.scm (operating-system-parameters-file): New procedure.
  (operating-system-derivation): Use it to produce a 'parameters' files.

system: Factorize GRUB menu entry label.

* gnu/system.scm (kernel->grub-label): New procedure.
  (operating-system-grub.cfg): Use it.

gnu: cursynth: Upgrade to 1.5.

* gnu/packages/cursynth.scm (cursynth)[source]: Upgrade to 1.5.  New
  'patches' field.
* gnu/packages/patches/cursynth-wave-rand.patch: New patch.
* gnu-system.am (dist_patch_DATA): Add it.

gnu: libmicrohttpd: Upgrade to 0.9.37.

* gnu/packages/gnunet.scm (libmicrohttpd): Upgrade to 0.9.37.

gnu: gnupg: Upgrade versions 1 and 2 (security fix.)

* gnu/packages/gnupg.scm (gnupg): Upgrade to 2.0.24.
  (gnupg-1): Upgrade to 1.4.17.

gnu: libgpg-error: Upgrade to 1.13.

* gnu/packages/gnupg.scm (libgpg-error): Upgrade to 1.13.

gnu: nano: Upgrade to 2.3.4.

* gnu/packages/nano.scm (nano): Upgrade to 2.3.4.

gnu: lightning: Upgrade to 2.0.4.

* gnu/packages/lightning.scm (lightning): Upgrade to 2.0.4.