bash completion: Complete 'guix gc' with file names.

Reported by a couple of cool folks at a bar in Brussels.

* etc/completion/bash/guix (_guix_complete): Use '_guix_complete_file'
for 'guix gc'.  This fixes completion of 'guix gc -d'.

file-systems: Add '%network-configuration-files' and '%network-file-mappings'.

* gnu/system/file-systems.scm (%network-configuration-files)
(%network-file-mappings): New variables.
* guix/scripts/environment.scm (%network-configuration-files): Remove.
(launch-environment/container): Refer to '%network-file-mappings'
instead of calling 'filter-map'.

gnu: bdb: Correct license.

* gnu/packages/databases.scm (bdb)[license]: Replace with up-to-date
information. Move previous contents to ...
(bdb-5.3)[license]: ... here.

gnu: dosfstools: Update to 4.1.

* gnu/packages/disk.scm (dosfstools): Update to 4.1.
[arguments]: Enable tests.
[native-inputs]: Add VIM.

gnu: grub: Update to 2.02rc1.

* gnu/packages/grub.scm (grub, grub-efi): Update to 2.02rc1.
[arguments]: Don't disable grub_func_test. Remove #:configure-flags.

gnu: certbot, python-acme: Update to 0.11.1.

* gnu/packages/tls.scm (python-acme, python2-acme): Update to 0.11.1.
(certbot): Update to 0.11.1.
[version]: Use python-acme's version.

gnu: tcpdump: Fetch source from tcpdump.org.

* gnu/packages/admin.scm (tcpdump)[source]: Remove temporary alternate URL.

gnu: ddrescue: Update to 1.22.

* gnu/packages/disk.scm (ddrescue): Update to 1.22.
[home-page]: Use HTTPS.

gnu: Add re2c.

* gnu/packages/re2c.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add re2c.scm.

CC: ng0 <contact.ng0@cryptolab.net>
Signed-off-by: Sergei Trofimovich <slyfox@inbox.ru>
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

config-daemon.ac: detect host AR

The problem is seen when we try to use explicit host:

    ./configure --prefix=/usr --localstatedir=/var/lib --host=x86_64-pc-linux-gnu
    make V=1

Before the change:
    ar cru libstore.a nix/libstore/libstore_a-gc.o
After the change:
    x86_64-pc-linux-gnu-ar cru libstore.a

* config-daemon.ac: use AM_PROG_AR to detect host AR

Signed-off-by: Sergei Trofimovich <slyfox@inbox.ru>
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

linux-container: Add comment on exception handling.

* gnu/build/linux-container.scm (run-container): Add note about writing
the exceptions.

linux-container: Do not rely on 'isatty?'.

This avoids problems where 'isatty?' return #t but 'ttyname' fails with
ENOTTY or such.

* gnu/build/linux-container.scm (mount-file-systems): Remove call of
'isatty?'.  Directly call 'ttyname' and catch 'system-error'.

gnu: xonsh: Update to 0.5.3.

* gnu/packages/shell.scm (xonsh): Update to 0.5.3.

gnu: u-boot: Update to 2017.01.

* gnu/packages/u-boot.scm (u-boot): Update to 2017.01.

gnu: u-boot: Use scandir.

* gnu/packages/u-boot.scm (make-u-boot-package): Modify.

gnu: imagemagick: Update to 6.9.7-7.

* gnu/packages/imagemagick.scm (imagemagick): Update to 6.9.7-7.

gnu: wget: Use libidn2.

Suggested by Efraim Flashner <efraim@flashner.co.il>.

Fixes support for internationalized domain names.

* gnu/packages/wget.scm (wget)[inputs]: Replace libidn with libidn2.

gnu: libidn2: Update to 0.16.

* gnu/packages/libidn.scm (libidn2): Update to 0.16.
[inputs]: Add libunistring.

gnu: linux-libre: Update to 4.9.8.

* gnu/packages/linux.scm (%linux-libre-version, %linux-libre-hash)
(linux-libre): Update to 4.9.8.

gnu: linux-libre@4.4: Update to 4.4.47.

* gnu/packages/linux.scm (linux-libre-4.4): Update to 4.4.47.