gnu: help2man: Update to 1.46.4.

* gnu/packages/man.scm (help2man): Update to 1.46.4.

gnu: global: Update to 6.3.3.

* gnu/packages/global.scm (global): Update to 6.3.3.

gnu: ucommon: Update to 6.2.3.

* gnu/packages/telephony.scm (ucommon): Update to 6.2.3.

gnu: cd-discid: Fix download location.

* gnu/packages/cdrom.scm (cd-discid): Fix download location.

gnu: Add git-test-sequence.

* gnu/packages/version-control.scm (git-test-sequence): New variable.

gnu: Add git-flow.

* gnu/packages/version-control.scm (git-flow, shflags): New variables.

gnu: wpa-supplicant: Remove dependency on DBus.

* gnu/packages/admin.scm (wpa-supplicant): Remove dependency on DBUS.

guix: scripts: Add GUIX_BUILD_OPTIONS environment handling.

* doc/guix.texi (Invoking guix build): Mention 'GUIX_BUILD_OPTIONS'.
* guix/scripts/archive.scm: (append args (environment-build-options)).
* guix/scripts/build.scm: Ditto.
* guix/scripts/environment.scm: Ditto.
* guix/scripts/package.scm: Ditto.
* guix/scripts/system.scm: Ditto.
* guix/ui.scm (environment-build-options): New function.
* guix/utils.scm (arguments-from-environment-variable): New function.
* tests/guix-build.sh: Add tests.
* test-env.in: Unset GUIX_BUILD_OPTIONS.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

daemon: Default to '--cores=0'.

Suggested by Deck Pickard <deck.r.pickard@gmail.com>.

* nix/nix-daemon/guix-daemon.cc (main): Set 'settings.buildCores' to 0.
* doc/guix.texi (Invoking guix-daemon): Adjust accordingly.

doc: Explain that 'file-system' must refer to mapped devices by file name.

* doc/guix.texi (File Systems): Clarify what to do when mapped devices
  are used.

Revert "system: Add a 'needed-for-boot?' field to 'mapped-device'."

This reverts commit 3b09332adf7ce8e976a4d117a62c586a53af04aa, which
turned out to be a bad idea because we need to have dependency
information between the device-mapping service and the file-system
service that uses it.

gnu: Add matplotlib.

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

services: xorg: Add 'xf86-video-sis'.

* gnu/services/xorg.scm (xorg-start-command)[xserver.conf]: Add
  ModulePath for 'xf86-video-sis'.

gnu-maintenance: Support .zip files.

Reported by Andreas Enge <andreas@enge.fr>.

* guix/gnu-maintenance.scm (sans-extension): Add case for ".zip".
  (%tarball-rx): Extend to handle .zip extension.

gnu: Add mg.

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

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

gnu: wireless-tools: Install the manual pages under $out/share/man.

* gnu/packages/linux.scm (wireless-tools)[origin]: Add snippet.

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

gnu: Add abcde.

* gnu/packages/cdrom.scm (abcde): New variable.

gnu: Add cd-discid.

* gnu/packages/cdrom.scm (cd-discid): New variable.

gnu: guix: Update snapshot.

* gnu/packages/package-management.scm (guix-devel): Update.

doc: Improve porting instructions.

* doc/guix.texi (Porting): Move 'glibc-dynamic-linker' paragraph above.
  Clarify what is meant by updating (gnu packages bootstrap).  Mention
  'gnu-system.am'.