gnu: Add dtach.

gnu/packages/screen.scm (dtach): New variable.

gnu: Add talloc.

* gnu/packages/samba.scm (talloc): New variable.

system: Use the default 'groups' field.

* gnu/system/install.scm (installation-os): Remove 'groups' field.
* build-aux/hydra/demo-os.scm: Likewise.

system: Augment the default set of groups.

* gnu/system/shadow.scm (%base-groups): New variable.
* gnu/system.scm (<operating-system>)[groups]: Use it as the default.

system: Remove useless 'members' field of 'user-group'.

* gnu/system/shadow.scm (<user-group>)[members]: Remove field.
* gnu/system/install.scm (installation-os)[users]: Remove 'members'
  fields.  Use 'supplementary-groups' for 'guest'.
* build-aux/hydra/demo-os.scm (users): Likewise.
* gnu/services/base.scm (guix-service): Remove 'members' field.

gnu: kmod: Honor $LINUX_MODULE_DIRECTORY.

* gnu/packages/patches/kmod-module-directory.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.
* gnu/packages/linux.scm (kmod)[origin]: Use it.

gnu: Add udev.

* gnu/packages/linux.scm (udev): New variable.
* gnu/packages/patches/udev-gir-libtool.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.

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

gnu: Add kmod.

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

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

gnu: man-pages: Upgrade to 3.69.

* gnu/packages/man.scm (man-pages): Upgrade to 3.69.

gnu: gnupg: Upgrade to 2.0.23.

* gnu/packages/gnupg.scm (gnupg): Upgrade to 2.0.23.

gnu: global: Upgrade to 6.3.

* gnu/packages/global.scm (global): Upgrade to 6.3.

Merge branch 'core-updates'

system: Prefer packages from %FINAL-INPUTS.

* gnu/packages/base.scm (canonical-package): New procedure.
* gnu/system.scm (%base-packages): Pass BASH, COREUTILS, FINDUTILS,
  GREP, and SED through 'canonical-package'.

gnu: isc-dhcp: In native builds, refer to the final Coreutils and sed.

* gnu/packages/admin.scm (isc-dhcp)[inputs]: Add Coreutils and sed only
  when (%current-target-system) is true.

gnu: privoxy: Use etc/privoxy as the sysconfdir.

Reported by "d00000" on #guix.

* gnu/packages/tor.scm (privoxy)[arguments]: Add #:configure-flags.

gnu: gawk: Apply work around to build system for MIPS.

* gnu/packages/gawk.scm (gawk): Work around a build problem on MIPS.

gnu: linux-libre: Upgrade to 3.15.

* gnu/packages/linux.scm (linux-libre): Upgrade to 3.15.

gnu: kbd: Patch buggy makefile.

* gnu/packages/linux.scm (kbd)[source]: Add 'modules' and 'snippet'
  fields.

gnu: guile-ncurses: Work around missing test files.

* gnu/packages/patches/guile-ncurses-tests.patch: New file.
* gnu/packages/guile.scm (guile-ncurses)[source]: Use it.
* gnu-system.am (dist_patch_DATA): Add it.

gnu: icu4c: Upgrade to 53.1.

* gnu/packages/icu4c.scm (icu4c): Upgrade to 53.1.