tests: Make sure 'guix archive --import' succeeds.

* tests/guix-archive.sh: Check the exit value of 'guix archive
  --import'.

daemon: Add tests for substitutes and --no-substitutes.

* tests/guix-daemon.sh: Add substituter tests.

daemon: Clear $NIX_SUBSTITUTERS when passed '--no-substitutes'.

* nix/nix-daemon/guix-daemon.cc (main): When --no-substitutes is used,
  clear NIX_SUBSTITUTERS.  Before that, and after
  89faa5c75cb3a419c6d02c51f56955275b7ae351, '--no-substitutes' would
  lead to attempts to use 'download-using-manifests.pl', which in
  practice would gracelessly fail.

daemon: Change some options via 'settings.set'.

* nix/nix-daemon/guix-daemon.cc (parse_opt): Use 'settings.set' instead
  of direct field access for 'buildCores', 'maxBuildJobs', and
  'useSubstitutes'.
  (main): Call 'settings.update' after 'argp_parse'.

gnu: tcl: Install man pages in share/man.

* gnu/packages/tcl.scm (tcl): Add --mandir configure flag.

Add (guix svn-download).

* guix/svn-download.scm, guix/build/svn.scm: New files.
* Makefile.am (MODULES): Add them.

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

gnu: gnu-pw-mgr: Fix download location.

* gnu/packages/gnu-pw-mgr.scm (gnu-pw-mgr): Fix download location.

gnu: Add mc

* gnu/packages/mc.scm: New file
* gnu/packages/patches/mc-fix-ncurses-build.patch: New patch
* gnu-system.am (GNU_SYSTEM_MODULES): Add mc.scm.
(dist_patch_DATA): Add patch

gnu: libssh2: Fix use with libssh2.pc

* gnu/packages/ssh.scm (libssh2): Pass --with-libgcrypt configure flag and
  propagate inputs.

Merge branch 'core-updates'

offload: Remove erroneous 'close-pipe' call.

* guix/scripts/offload.scm (send-files): Remove 'close-pipe' call from
  'guard' handler ('pipe' here referred to Guile's 'pipe' procedure.)

offload: Wait for the processes involved in 'guix archive --missing'.

* guix/scripts/offload.scm (send-files): Keep the second return value of
  'filtered-port'.  Call 'waitpid' on it.

gnu: gp2c: Upgrade to 0.0.8pl1.

* gnu/packages/algebra.scm (gp2c): Upgrade to 0.0.8pl1, add native input perl.

offload: Allow one transfer in each direction simultaneously.

* guix/scripts/offload.scm (transfer-and-offload): Use 'upload' lock
  instead of 'bandwidth' around 'send-files' calls, and 'download' lock
  around 'retrieve-files' call.

offload: Disable SSH-level compression.

* guix/scripts/offload.scm (remote-pipe): Remove '-z' lsh command line
  argument.  This makes transfers almost an order of magnitude slower.
  OpenSSH's ssh(1) man page notes: "Compression is desirable on modem lines
  and other slow connections, but will only slow down things on fast
  networks."  See also
  <http://www.spikelab.org/blog/transfer-largedata-scp-tarssh-tarnc-compared.html>.

gnu: pari-gp: Upgrade to 2.7.0.

* gnu/packages/algebra.scm (pari-gp): Upgrade to 2.7.0.

gnu: gnu-pw-mgr: Upgrade to 1.2

* gnu/packages/gnu-pw-mgr.scm: Upgrade to 1.2

check-available-binaries: Make sure substitutes are enabled.

* build-aux/check-available-binaries.scm: Add call to
  'set-build-options'.

hydra: Hard-code target systems.

* build-aux/hydra/gnu-system.scm (hydra-jobs)[systems]: Define locally,
  independently of ARGUMENTS.  This matches the new Hydra convention,
  where using a 'system' input is deprecated.

gnu: guile-ssh: Upgrade to 0.6.0.

* gnu/packages/ssh.scm (guile-ssh): Upgrade to 0.6.0.
  [arguments]: Remove #:tests? #f; add #:parallel-build? #f.