Merge branch 'master' into gtk-rebuild

Conflicts:
	gnu/packages/gtk.scm

services: swap: Use 'restart-on-EINTR'.

* gnu/services/base.scm (swap-service)[start, stop]: Use 'restart-on-EINTR'.
* guix/build/syscalls.scm (swapoff): Fix typo in 'throw' arguments.

services: xorg: Add xf86-input-libinput to the server's module path.

* gnu/services/xorg.scm (xorg-configuration-file): Add XF86-INPUT-LIBINPUT.

services: xorg: Assume STARTX is a regular value.

* gnu/services/xorg.scm (slim-service): Expect STARTX to be a regular value,
  not a monadic value.

services: xorg: Allow extra config text to be added verbatim.

* gnu/services/xorg.scm (xorg-configuration-file): Add #:extra-config and
  honor it.
* doc/guix.texi (X Window): Adjust accordingly.

services: xorg: Make 'xorg-configuration-file' public.

* gnu/services/xorg.scm (xorg-configuration-file): New procedure, with code
  formerly in 'xorg-start-command'.
  (xorg-start-command): Remove #:drivers and #:resolutions; add
  #:configuration-file; use it as well as 'xorg-configuration-file'.

services: dhcp-client: Turn up the interfaces before calling 'dhclient'.

Somehow, as of Linux 4.0.2, the interfaces are down by default, which
prevents 'dhclient' from actually using them.

* gnu/services/networking.scm (dhcp-client-service): Call
  'set-network-interface-up' on each item of IFACES.

services: dhcp-client: Better track dhclient's PID.

* gnu/services/networking.scm (dhcp-client-service)[start]: Remove
  PID-FILE first.  When 'call-with-input-file' throws ENOENT, try
  again.

doc: Document 'avahi-service'.

* gnu/services/avahi.scm (avahi-service): Add URL in docstring.
* doc/guix.texi (Networking Services): Document it.
  (Name Service Switch): Fix cross-reference.

doc: Document sessions and ~/.xsession for SLiM.

* gnu/services/xorg.scm (slim-service): Document session types and
  ~/.xsession.
* doc/guix.texi (X Window): Adjust accordingly.

services: Add '%desktop-services'.

* gnu/services/desktop.scm (%desktop-services): New variable.
* doc/guix.texi (Desktop Services): Document it.

artwork: Update to latest version.

* gnu/artwork.scm (%artwork-repository): Update.
* gnu/services/xorg.scm (%default-slim-theme-name): Change to "0.x".
* gnu/system/grub.scm (%background-image): Change to
  GuixSD-fully-black-4-3.svg.

gnu: Add postgresql-service.

* gnu/services/databases.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.
* doc/guix.texi ("Database Services"): New subsubsection.

services: Group desktop services in (gnu services desktop).

* gnu/services/colord.scm, gnu/services/dbus.scm,
  gnu/services/upower.scm: Remove.
* gnu/services/desktop.scm: New file, with contents taken from the above
  files.
* gnu-system.am (GNU_SYSTEM_MODULES): Adjust accordingly.
* doc/guix.texi (Desktop Services): New section.
  (Various Services): Move colord-service and upower-service from
  here to "Desktop Services".

services: Add console-keymap service.

* gnu/services/base.scm (console-keymap-service): New procedure.
* doc/guix.texi (Base Services): Document it.

Co-authored-by: 宋文武 <iyzsong@gmail.com>

file-systems: Use a second 'mount' call for read-only bind mounts.

* gnu/build/file-systems.scm (MS_REMOUNT): New constant.
  (mount-file-system): Add 'flags' local variable.   When FLAGS has
  MS_BIND & MS_RDONLY, call 'mount' with MS_REMOUNT.
* gnu/services/base.scm (file-system-service) <start>: Likewise.

Merge branch 'core-updates'

Merge branch 'master' into core-updates

Conflicts:
	gnu-system.am
	gnu/packages/gstreamer.scm

services: Explicitly refer to Shadow when requiring the 'nologin' shell.

* gnu/services/avahi.scm (avahi-service): Change 'shell' to a gexp
  referring to "nologin" in the SHADOW package.
* gnu/services/dbus.scm (dbus-service): Likewise.
* gnu/services/networking.scm (ntp-service, tor-service): Likewise.

Merge branch 'master' into core-updates