offload: Drop 'remote-pipe'.

* guix/scripts/offload.scm (remote-pipe): Remove.
(machine-load): Use 'open-remote-pipe*' instead of 'remote-pipe'.

offload: Rewrite to make direct RPCs to the remote daemon.

* guix/scripts/offload.scm (<build-machine>)[daemon-socket]: New field.
(connect-to-remote-daemon): New procedure.
(%gc-root-file, register-gc-root, remove-gc-roots, offload): Remove.
(transfer-and-offload): Rewrite using 'connect-to-remote-daemon' and
RPCs over SSH.
(store-import-channel, store-export-channel): New procedures.
(send-files, retrieve-files): Rewrite using these.

offload: Remove 'with-nar-error-handling' macro.

* guix/scripts/offload.scm (with-nar-error-handling): Remove.
(guix-offload): Use 'with-error-handling' instead.

store: 'open-connection' can taken an open port.

* guix/store.scm (open-unix-domain-socket): New procedure.
(open-connection): Add #:port parameter and honor it.

offload: Reuse SSH session during 'transfer-and-offload'.

* guix/scripts/offload.scm (remote-pipe): Replace 'machine' parameter
with 'session'.  Remove 'open-ssh-session' call.
(register-gc-root): Replace 'machine' with 'session'.  Use '
session-get' instead of 'build-machine-name'.
(remove-gc-roots, offload, send-files, retrieve-files): Likewise.
(transfer-and-offload): Add 'open-ssh-session' call.  Handle 'offload'
errors here.
(machine-load): Add call to 'open-ssh-session'.

offload: Use Guile-SSH instead of GNU lsh.

* guix/scripts/offload.scm (<build-machine>)[ssh-options]: Remove.
[host-key, host-key-type]: New fields.
(%lsh-command, %lshg-command, user-lsh-private-key): Remove.
(user-openssh-private-key, private-key-from-file*): New procedures.
(host-key->type+key, open-ssh-session): New procedures.
(remote-pipe): Remove 'mode' parameter.  Rewrite in terms of
'open-ssh-session' etc.  Update users.
(send-files)[missing-files]: Rewrite using the bidirectional channel
port.
Remove call to 'call-with-compressed-output-port'.
(retrieve-files): Remove call to 'call-with-decompressed-port'.
(machine-load): Remove exit status logic.
* doc/guix.texi (Requirements): Mention Guile-SSH.
(Daemon Offload Setup): Document 'host-key' and 'private-key'.  Show the
default value on each @item line.
* m4/guix.m4 (GUIX_CHECK_GUILE_SSH): New macro.
* config-daemon.ac: Use 'GUIX_CHECK_GUILE_SSH'.  Set
'HAVE_DAEMON_OFFLOAD_HOOK' as a function of that.

gnu: guile-ssh: Update to 0.10.2.

* gnu/packages/ssh.scm (guile-ssh): Update to 0.10.2.
[home-page]: Update.
[source]: Use the 'url-fetch' method and a GitHub generated
tarball.
[arguments] <autoreconf>: Remove now unneeded 'chmod' call.

gnu: hydrogen: Update to 0.9.7.

* gnu/packages/music.scm (hydrogen): Update to 0.9.7.

gnu: btrfs-progs: Update to 4.8.4.

* gnu/packages/linux.scm (btrfs-progs): Update to 4.8.4.

gnu: lz4: Update to 1.7.4.2.

* gnu/packages/compression.scm (lz4): Update to 1.7.4.2.

gnu: hplip: Update to 3.16.11.

* gnu/packages/cups.scm (hplip): Update to 3.16.11.

gnu: qtractor: Update to 0.8.0.

* gnu/packages/music.scm (qtractor): Update to 0.8.0.

gnu: qemu: Install all required info files.

* gnu/packages/qemu.scm (qemu)[arguments]: Adjust 'install-info' phase
to find all info files (including "*.info-N").

gnu: Add kicad-library.

* gnu/packages/engineering.scm (kicad-library): New variable.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu: Add kicad.

* gnu/packages/engineering.scm (kicad): New variable.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu: Add python2-wxpython.

* gnu/packages/wxwidgets.scm (python2-wxpython): New variable.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu: Add wxwidgets-gtk2.

* gnu/packages/wxwidgets.scm (wxwidgets-gtk2): New variable.

Signed-off-by: Leo Famulari <leo@famulari.name>

gnu: nginx: Update to 1.11.6.

* gnu/packages/web.scm (nginx): Update to 1.11.6.
[arguments]: Remove the obsolete option --with-ipv6 from #:configure-flags.

gnu: miniupnpc: Improve synopsis and description.

* gnu/packages/upnp.scm (miniupnp)[synopsis, description]: Edit, fix typos,
add some relevant (search) terms from the home page, and expand acronyms.

gnu: miniupnpc: Use the correct ‘upnpc’ in ‘external-ip’.

* gnu/packages/upnp.scm (miniupnpc)[arguments]: Add ‘qualify-paths’ phase.