gnu: games: Add new package gnubg

* gnu/packages/games.scm (gnubg): New variable

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

gnu: libgcrypt: Add "debug" output.

* gnu/packages/gnupg.scm (libgcrypt): Add 'outputs' field.

archive: Add '--authorize'.

* guix/scripts/archive.scm (authorize-key): New procedure.
  (guix-archive): Call it when OPTS contains 'authorize-key'.
* tests/guix-archive.sh: Add test with invalid public key.
* guix/pki.scm: Export '%acl-file'.
* doc/guix.texi (Invoking guix archive): Make it clear that '--import'
  works only with authorized keys.  Document '--authorize'.

archive: Add '--generate-key'.

* guix/pk-crypto.scm (error-source, error-string): New procedures.
* guix/pki.scm (%private-key-file): New variable.
* guix/scripts/archive.scm (show-help): Document '--generate-key'.
  (%options): Add "generate-key".
  (generate-key-pair): New procedure.
  (guix-archive): Call 'generate-key' when OPTS contains a
  'generate-key' pair.
* doc/guix.texi (Setting Up the Daemon): Suggest generating a key pair.
  (Invoking guix archive): Document '--generate-key'.

pk-crypto: Fix 'canonical-sexp->sexp' for atoms.

* guix/pk-crypto.scm (canonical-sexp->sexp): Add hack to extract an
  atom's buffer.
* tests/pk-crypto.scm ("sexp->canonical-sexp->sexp"): Add sample.

pk-crypto: Work around Libgcrypt bug <https://bugs.g10code.com/gnupg/issue1594>.

* guix/pk-crypto.scm (canonical-sexp-fold): Call 'nth-data' before
  'nth' to work around <https://bugs.g10code.com/gnupg/issue1594>.
* tests/pk-crypto.scm ("https://bugs.g10code.com/gnupg/issue1594"): New
  test.

authenticate: Consistently use 'leave' for fatal error reporting.

* guix/scripts/authenticate.scm (guix-authenticate): Replace all uses of
  'format' + 'exit' with 'leave'.

Thank Kete.

gnu: mesa: Move out of xorg.scm and into gl.scm

* gnu/packages/xorg.scm (mesa): Move to...
* gnu/packages/gl.scm (mesa): ... here.  New variable.
* gnu/packages/gnome.scm, gnu/packages/gnuzilla.scm,
  gnu/packages/qemu.scm, gnu/packages/qt.scm: Adjust accordingly.

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

doc: Invoke 'useradd' with '--system'.

Reported by Kete <kete@ninthfloor.org>.
Fixes <http://bugs.gnu.org/16289>.

* doc/guix.texi (Setting Up the Daemon): Add '--system' to the 'useradd'
  command line.  Suggested by Kete <kete@ninthfloor.org>.

gnu: automake: Upgrade to 1.14.1.

* gnu/packages/autotools.scm (automake): Upgrade to 1.14.1.

gnu: gdbm: Upgrade to 1.11.

* gnu/packages/gdbm.scm (gdbm): Upgrade to 1.11.

build: Improve documentation of Nix-related options.

* configure.ac: Add documentation for --with-nix and --with-nixpkgs.

gnu: games: New module

* gnu/packages/games.scm (gnubik): New variable

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

gnu: gnome: Add new package gtkglext

* gnu/packages/gnome.scm (gtkglext): New variable.
* gnu/packages/patches/gtkglext-disable-disable-deprecated.patch,
  gnu/packages/patches/gtkglext-remove-pangox-dependency.patch: New
  files.
* gnu-system.am (dist_patch_DATA): Add them.

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

authenticate: Disallow imports signed with unauthorized keys.

* guix/scripts/authenticate.scm (signature-sexp): Remove.
  (guix-authenticate): Upon '-verify', check whether the signature's
  public key passes 'authorized-key?'.

Add (guix pki).

* guix/pki.scm, tests/pki.scm: New files.
* Makefile.am (MODULES): Add 'guix/pki.scm'.
  (SCM_TESTS): Add 'tests/pki.scm'.

config: Export '%config-directory'.

* configure.ac: Define and substitute 'guix_sysconfdir'.
* guix/config.scm.in (%config-directory): New variable.

Move 'with-atomic-file-output' to (guix utils).

* guix/scripts/substitute-binary.scm (with-atomic-file-output): Move to...
* guix/utils.scm (with-atomic-file-output): ... here.

pk-crypto: Add canonical-sexp to sexp conversion procedures.

* guix/pk-crypto.scm (canonical-sexp-fold, canonical-sexp->sexp,
  sexp->canonical-sexp): New procedures.
* tests/pk-crypto.scm ("canonical-sexp->sexp",
  "sexp->canonical-sexp->sexp"): New tests.