gnu: linux-libre: Update to 3.16.3.

* gnu/packages/linux.scm (linux-libre): Update to version 3.16.3.

system: Add udev rule for /dev/kvm.

* gnu/services/base.scm (kvm-udev-rule): New procedure.
  (udev-service): Use it, and add it to RULES.
  (guix-build-accounts): Add "kvm" to the 'supplementary-groups' field.
* gnu/system/shadow.scm (%base-groups): Add "kvm".

linux-initrd: Remove now obsolete #:guile-modules-in-chroot? parameter.

* gnu/build/linux-boot.scm (boot-system): Remove
  #:guile-modules-in-chroot? and related code.
* gnu/system/linux-initrd.scm (base-initrd): Likewise.
* gnu/system/vm.scm (expression->derivation-in-linux-vm): Remove
  #:guile-modules-in-chroot? argument in 'base-initrd' call.

doc: Remove a couple of limitations.

* doc/guix.texi (System Installation): Remove encrypted disks and swap
  from the limitations.

system: Add support for swap devices.

* gnu/services/base.scm (swap-service): New procedure.
* gnu/system.scm (<operating-system>)[swap-devices]: New field.
  (swap-services): New procedure.
  (essential-services): Use it.

syscalls: Add 'swapon' and 'swapoff'.

* guix/build/syscalls.scm (swapon, swapoff): New procedures.
* tests/syscalls.scm ("swapon, ENOENT/EPERM", "swapoff, EINVAL/EPERM"):
  New tests.

doc: Document mapped devices.

* doc/guix.texi (Mapped Devices): New subsection.

system: Define 'device-mapping-kind', and add a 'close' procedure.

* gnu/system/file-systems.scm (<mapped-device-type>): New record type.
  (<mapped-device>)[command]: Remove field.
  [type]: New field.
* gnu/services/base.scm (device-mapping-service): Rename 'command'
  parameter to 'open'.  Add 'close' parameter and honor it.
* gnu/system.scm (luks-device-mapping): Rename to...
  (open-luks-device): ... this.
  (close-luks-device): New procedure.
  (luks-device-mapping): New variable.
  (device-mapping-services): Get the type of MD, and pass its 'open' and
  'close' fields to 'device-mapping-service'.

pull: Rewrite using gexps.

* guix/scripts/pull.scm (unpack): Remove 'store' parameter.  Rewrite
  using 'gexp->derivation'.
  (what-to-build, indirect-root-added, build-and-install): New
  procedures.
  (guix-pull): Use it.

gnu: skribilo: Make sure Guile-Reader is in the search path.

Reported by Luis Souto Graña <luissoutobueu@gmail.com>.

* gnu/packages/skribilo.scm (skribilo)[arguments]: Add #:phases.

gnu: libcanberra: Update URL.

Reported by Federico Beffa <beffa@ieee.org>.

* gnu/packages/libcanberra.scm (libcanberra)[source]: Update URI.

services: dhcp-client: Start 'dhclient' in "no wait" mode.

* gnu/services/networking.scm (dhcp-client-service): Pass '-nw' to
  'dhclient'.

services: file-system: Change directory to root before unmounting.

* gnu/services/base.scm (file-system-service)[stop]: Add 'chdir' call.

services: user-processes: Wait for complete process termination.

* gnu/services/base.scm (user-processes-service): Add 'wait' loop.

services: udev: Make non-respawnable.

* gnu/services/base.scm (udev-service): Add 'respawn?' field.

services: Change default 'stop' value to #~(const #f).

* gnu/services.scm (<service>)[stop]: Change default value.

build: Ignore the user's language settings when running tests.

* test-env.in: Unset 'LANGUAGE', set 'LC_MESSAGE'.

utils: Create temporary files in $TMPDIR or /tmp.

Reported by Federico Beffa <beffa@ieee.org>.

* guix/utils.scm (call-with-temporary-output-file): Prepend $TMPDIR or
  /tmp to TEMPLATE.

system: Add "input" to '%base-groups'.

* gnu/system/shadow.scm (%base-groups): Add "input" group.

Remove outdated items from 'TODO'.