ui: Add 'display-hint'.

* guix/ui.scm (known-variable-definition): New procedure.
(report-load-error): Use it.

gnu: %intel-compatible-systems: Re-add variable.

This is a follow-up to cfbe7b7f4ccdb61534b47d91fe8e43db2ee1737d.

* gnu/packages/linux.scm (%intel-compatible-systems): New variable.

gnu: linux: Add linux-libre arm kernel.

* Makefile.am (AUX_FILES): Add arm config file.
* gnu/packages/aux-files/linux-libre/4.13-arm.conf: New file.
* gnu/packages/linux.scm (%intel-compatible-systems): Rename to
  %linux-compatible-systems and add "armhf-linux".
  (linux-libre): Adapt consequently.

The config file for arm is taken from debian armmp kernel. It's a generic
firmware for ARMv7 multiplatform compatible SoCs.

gnu: chromaprint: Update to 1.4.2.

* gnu/packages/mp3.scm (chromaprint): Update to 1.4.2.

gnu: libwnck: Update to 3.24.1.

* gnu/packages/gnome.scm (libwnck): Update to 3.24.1.

system: Do not set 'TZ'.

Fixes <https://bugs.gnu.org/29212>.
Reported by Diego Nicola Barbato <dnbarbato@posteo.de>.

* gnu/system.scm (operating-system-environment-variables): Remove "TZ".

gnu: roary: Update to 3.11.0.

* gnu/packages/bioinformatics.scm (roary): Update to 3.11.0.
[inputs]: Add perl-digest-md5-file.

gnu: totem: Enable parallel build.

* gnu/packages/gnome.scm (totem)[arguments]: Set #:parallel-build? to #t
implicitly.

gnu: tremc: Update to 0.9.0-1.9755b50.

* gnu/packages/bittorrent.scm (tremc): Update to 0.9.0-1.9755b50.
[version]: Use git-version.
[source]: Use git-file-name.

gnu: slurm: Update to 16.05.11 [fixes CVE-2017-15566].

* gnu/packages/parallel.scm (slurm): Update to 16.05.11.
[source]: Use the recommended download URL.

gnu: rpm: Update to 4.13.0.2 [fixes CVE-2017-{7500,7501}].

* gnu/packages/package-management.scm (rpm): Update to 4.13.0.2.

gnu: python-icalendar: Update to 4.0.0.

* gnu/packages/python.scm (python-icalendar): Update to 4.0.0.

gnu: syncthing: Update to 0.14.40.

* gnu/packages/syncthing.scm (syncthing): Update to 0.14.40.
[inputs]: Add go-github-com-zillode-notify.

gnu: Add go-github-com-zillode-notify.

* gnu/packages/syncthing.scm (go-github-com-zillode-notify): New variable.

gnu: go-github-com-audriusbutkevicius-kcp-go: Update to 0.0.0-1.8ae5f52.

* gnu/packages/syncthing.scm (go-github-com-audriusbutkevicius-kcp-go):
Update to 0.0.0-1.8ae5f52.
[propagated-inputs]: Add go-github-com-tjfoc-gmsm-sm4.

gnu: Add go-github-com-tjfoc-gmsm-sm4.

* gnu/packages/syncthing.scm (go-github-com-tjfoc-gmsm-sm4): New variable.

gnu: Improve error reporting of the use-.*modules macros.

Suggested by Julien Lepiller and myglc2
at <https://lists.gnu.org/archive/html/guix-devel/2017-11/msg00106.html>.

* gnu.scm (%try-use-modules): New procedure.
(package-module-hint, service-module-hint): New procedures.
(try-use-modules): New macro.
(use-package-modules, use-service-modules, use-system-modules): Use it.
* tests/guix-system.sh: Test it.

services: Add 'lookup-service-types'.

* gnu/services.scm (lookup-service-types): New procedure.
* tests/services.scm ("lookup-service-types"): New test.

services: 'fold-service-types' includes (gnu services).

* gnu/services.scm (all-service-modules): New procedure.
(fold-service-types): Use it for the default MODULES value.

services: 'fold-service-types' honors its seed.

* gnu/services.scm (fold-service-types): Use SEED instead of '().