build: Adjust 'courage level' of different systems.

* m4/guix.m4 (GUIX_ASSERT_SUPPORTED_SYSTEM): Add i586-gnu. Move
powerpc-linux to unsupported but not needing courage. Add mips64el-linux
to unsupported.

build-system: emacs: Do not rely on input labels in the 'build' phase.

This commit repairs the Emacs build system for packages using the new
label-less "guix style".  Tested with emacs-libgit.

* guix/build/emacs-build-system.scm (build): Use search-input-file to locate
emacs.

gnu: icecat-source: Enable xz parallel compression.

* gnu/packages/gnuzilla.scm (icecat-source): Set XZ_DEFAULTS to
%xz-parallel-args to enable parallel compression and hasten the build.  Remove
trailing #t.

guix: Fix typo in last commit.

* guix/build/emacs-build-system.scm (make-autoloads): Fix typo.

guix: Do not assume "emacs" label in make-autoloads.

* guix/build/emacs-build-system.scm (make-autoloads): Look for "emacs"
executable independently on the label.

news: Add 'de' translation.

* etc/news.scm: Add German translation of static networking entry.

gnu: texlive-fira: Update hash.

* gnu/packages/tex.scm (texlive-fira): Update hash.

gnu: texlive-latex-textpos: Update hash.

* gnu/packages/tex.scm (texlive-latex-textpos): Update hash.

gnu: texlive-translator: Fix hash.

* gnu/packages/tex.scm (texlive-translator): Fix hash.

gnu: eigen-for-tensorflow: Build with GCC 7.

* gnu/packages/algebra.scm (eigen-for-tensorflow)[native-inputs]: Add gcc-7.

gnu: tensorflow: Do not unpack directory.

* gnu/packages/machine-learning.scm (tensorflow)[arguments]: Copy Eigen source
code instead of trying to unpack it.

gnu: python2-entrypoints: Add missing input.

* gnu/packages/python-xyz.scm (python2-entrypoints)[propagated-inputs]: Add
python2-configparser.
(python-entrypoints)[properties]: Add python2-variant.

gnu: Remove input labels.

* gnu/packages/emacs-xyz.scm (emacs-geiser-guile)[propagated-inputs]:
* gnu/packages/emacs-xyz.scm (emacs-geiser-gauche)[native-inputs]:
* gnu/packages/emacs-xyz.scm (emacs-geiser-racket)[propagated-inputs]:
* gnu/packages/emacs-xyz.scm (emacs-libgit)[native-inputs]:
* gnu/packages/emacs-xyz.scm (emacs-ghub)[native-inputs]:
* gnu/packages/emacs-xyz.scm (emacs-ample-regexps)[native-inputs]:
* gnu/packages/emacs-xyz.scm (emacs-relative-buffers)[native-inputs]:
* gnu/packages/emacs-xyz.scm (emacs-w3m)[native-inputs]: Remove labels.

gnu: quadrapassel: Remove input labels.

* gnu/packages/games.scm (quadrapassel)[native-inputs]: Remove labels
from inputs.

gnu: quadrapassel: Update to 40.2.

* gnu/packages/games.scm (quadrapassel): Update to 40.2.

gnu: libraqm: Update to 0.8.0.

* gnu/packages/fontutils.scm (libraqm): Update to 0.8.0.

gnu: cuirass: Update to 1.1.0-7.7160b18.

* gnu/packages/ci.scm (cuirass): Update to 1.1.0-7.7160b18.

gnu: qutebrowser: Update to 2.4.0.

* gnu/packages/web-browsers.scm (qutebrowser): Update to 2.4.0.
[arguments]: Remove trailing #t.

gnu: qutebrowser: Satisfy guix lint.

* gnu/packages/web-browsers.scm (qutebrowser)[inputs]: Add bash-minimal.

gnu: lagrange: Add 'release-monitoring-url' property.

* gnu/packages/web-browsers.scm (lagrange)[properties]: New field.