tests: Deal with 'mount-points' not returning "/".

Fixes <http://bugs.gnu.org/20261>.
Reported by Mark H Weaver <mhw@netris.org>.

* tests/syscalls.scm ("mount-points"): Check for a few other likely
  mount points in addition to "/".

gnu: lsof: Add mirrors.

Reported by Tomáš Čech.

* gnu/packages/lsof.scm (lsof)[source]: Add two mirrors.

guix package: Move generation deletion to its own procedure.

* guix/scripts/package.scm (delete-matching-generations): New procedure,
  with code formerly found...
  (guix-package)[process-actions]: ... here.  Use it.
  Remove 'current-generation-number'.

gnu: Perl GD: Add real patch.

Replaces the stub patch added in 43754738e030a4083b0881b2264b905bc563e78b.

* gnu/packages/patches/perl-gd-options-passthrough-and-fontconfig.patch:
  Update patch.

43754738e030a4083b0881b2264b905bc563e78b

gnu: icecat: Fix source URI.

* gnu/packages/gnuzilla.scm (icecat)[source]: Fix source URI computation.

gnu: icecat: Update to 31.6.0-gnu1.

* gnu/packages/patches/icecat-CVE-2015-0801.patch,
  gnu/packages/patches/icecat-CVE-2015-0807.patch,
  gnu/packages/patches/icecat-CVE-2015-0815-pt1.patch,
  gnu/packages/patches/icecat-CVE-2015-0815-pt2.patch,
  gnu/packages/patches/icecat-CVE-2015-0815-pt3.patch,
  gnu/packages/patches/icecat-CVE-2015-0816.patch,
  gnu/packages/patches/icecat-CVE-2015-0817.patch,
  gnu/packages/patches/icecat-CVE-2015-0818-pt1.patch,
  gnu/packages/patches/icecat-CVE-2015-0818-pt2.patch,
  gnu/packages/patches/icecat-bug-1127780.patch,
  gnu/packages/patches/icecat-bug-1145870.patch: Remove files.
* gnu-system.am (dist_patch_DATA): Remove them.
* gnu/packages/gnuzilla.scm (icecat): Update to 31.6.0-gnu1.  Remove patches.

gnu: nss: Update to 3.18.

* gnu/packages/gnuzilla.scm (nss): Update to 3.18.  Compute source URI
  automatically based on version.

Remove unused module import (gnu packages ed) from (gnu packages commencement).

* gnu/packages/commencement.scm: Remove (gnu packages ed) module import.

gnu: emacs: Add librsvg to inputs.

* gnu/packages/emacs.scm (emacs)[inputs]: Add librsvg.
  (emacs-no-x)[inputs]: Remove librsvg from inherited inputs.

gnu: linux-libre: Fix drm_wait_one_vblank warnings.

* gnu/packages/patches/linux-libre-vblank-fix.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.
* gnu/packages/linux.scm (linux-libre)[source]: Add patch.

gnu: Add glib-networking.

* gnu/packages/gnome.scm (glib-networking): New variable.

linux-initrd: Add virtio drivers by default.

* gnu/system/linux-initrd.scm (base-initrd): Change #:virtio? default
  to #t.  This will facilitate the use of GuixSD in VM guests.

Add Andy to 'AUTHORS'.

system: Take kernel modules from the user-specified kernel.

* gnu/system/linux-initrd.scm (base-initrd): Add #:linux option to
  specify the linux kernel to use.
* gnu/system/vm.scm (expression->derivation-in-linux-vm): Propagate
  #:linux to base-initrd.
* gnu/system.scm (operating-system-initrd-file): Pass #:linux to
  'make-initrd'.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

gnu: nginx: Clean up installation directories.

* gnu/packages/web.scm (nginx): Add 'fix-root-dirs' phase.

gnu: nginx: Use modify-phases syntax.

* gnu/packages/web.scm (nginx): Use modify-phases syntax.

gnu: Add livestreamer.

* gnu/packages/video.scm (livestreamer): New variable.

gnu: Add python-singledispatch.

* gnu/packages/python.scm (python-singledispatch, python2-singledispatch): New
  variables.

gnu: python-requests: Fix Python 2 version and add support for Python 3.

* gnu/packages/python.scm (python-requests): New variable.
  (python2-requests): Generate based on Python 3 variant.

gnu: gnome-mines: Update to 3.16.0.

* gnu/packages/gnome.scm (gnome-mines): Update to 3.16.0.