gnu-maintenance: Correctly compare versions.

* guix/gnu-maintenance.scm (latest-gnu-release): Add calls to
'sans-extension'.  This fixes version comparison, which could be fooled
with the ".tar.gz" extension.

gnu: guix: Update snapshot.

* gnu/packages/package-management.scm (guix): Update to a9468b4.

substitute: Download from unauthorized sources that provide the right content.

This allows substitutes to be downloaded from unauthorized servers, as
long as they advertise the same hash and references as one of the
authorized servers.

* guix/scripts/substitute.scm (assert-valid-narinfo): Remove.
(valid-narinfo?): Add #:verbose?.  Handle each case of
'signature-case'.
(equivalent-narinfo?): New procedure.
(lookup-narinfos/diverse): Add 'authorized?' parameter and honor it.
[select-hit]: New procedure.
(lookup-narinfo): Add 'authorized?' parameter and pass it.
(process-query): Adjust callers accordingly.
(process-substitution): Remove call to 'assert-valid-narinfo'.  Check
whether 'lookup-narinfo' returns true and call 'leave' if not.
* tests/substitute.scm (%main-substitute-directory)
(%alternate-substitute-directory): New variables.
(call-with-narinfo): Make 'narinfo-directory' a parameter.  Call
'mkdir-p' to create it.  Change unwind handler to check whether
CACHE-DIRECTORY exists before deleting it.
(with-narinfo*): New macro.
("substitute, no signature")
("substitute, invalid hash")
("substitute, unauthorized key"): Change expected error message to "no
valid substitute".
("substitute, unauthorized narinfo comes first")
("substitute, unsigned narinfo comes first")
("substitute, first narinfo is unsigned and has wrong hash")
("substitute, first narinfo is unsigned and has wrong refs")
("substitute, unsigned narinfo comes first")
("substitute, two invalid narinfos"): New tests.
* doc/guix.texi (Substitutes): Explain the new behavior.

substitute: Make substitute URLs a SRFI-39 parameter.

* guix/scripts/substitute.scm (%cache-urls): Rename to...
(%default-substitute-urls): ... this.
(substitute-urls): New variable.
(guix-substitute): Use it instead of %CACHE-URLS.
* tests/substitute.scm: Likewise.

gnu: Add monero-core.

* gnu/packages/finance.scm (monero-core): New variable.

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

gnu: Add monero.

* gnu/packages/finance.scm (monero): New variable.

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

gnu: libffcall: Update to 2.0.

* gnu/packages/libffcall.scm (libffcall): Update to 2.0.

gnu: linux-libre: Update to 4.13.1.

* gnu/packages/linux.scm (%linux-libre-version): Update to 4.13.1.
(%linux-libre-hash): Update hash.

gnu: linux-libre@4.9: Update to 4.9.49.

* gnu/packages/linux.scm (linux-libre-4.9): Update to 4.9.49.

gnu: python-apsw: Build with all extensions.

* gnu/packages/python.scm (python-apsw)[phases]: Replace build phase; add flag
  to build all extensions. Add build-test-helper to allow testing of
  extensions.

gnu: gnome-sudoku: Update to 3.26.0.

* gnu/packages/gnome.scm (gnome-sudoku): Update to 3.26.0.

gnu: gnome-klotski: Update to 3.22.2.

* gnu/packages/gnome.scm (gnome-klotski): Update to 3.22.2.

gnu: libgnome-games-support: Update to 1.2.3.

* gnu/packages/gnome.scm (libgnome-games-support): Update to 1.2.3.

gnu: cloc: Fix typo in description.

* gnu/packages/code.scm (cloc)[description]: Fix typo.

gnu: cloc: Update to 1.74.

* gnu/packages/code.scm (cloc): Update to 1.74.
[source]: Update source URL.

gnu: youtube-dl: Update to 2017.09.10.

* gnu/packages/video.scm (youtube-dl): Update to 2017.09.10.

gnu: Fix build failures caused by commit
d10092b849153dc27cfed0a9601fde6c7bdec918.

* gnu/packages/bioinformatics.scm (seek)[arguments]: Restore previous phase
order.
* gnu/packages/ci.scm (cuirass)[arguments]: Add patch-/bin/sh phase.

install: Add OpenSSH to the global profile.

Suggested by Jan Nieuwenhuizen.

* gnu/system/install.scm (installation-os)[packages]: Add OPENSSH.

install: Add 'passwd' to $PATH.

Suggested by Jan Nieuwenhuizen.

* gnu/system/install.scm (installation-os)[setuid-programs]: Add 'passwd'.

gnu: Add emacs-bash-completion.

* gnu/packages/emacs.scm (emacs-bash-completion): New variable.