gnu: Build wiredtiger with snappy support.

This is probably necessary to get the MongoDB package in Guix to successfully
use the Guix wiredtiger package, as MongoDB it uses wiredtiger with snappy by
default.

* gnu/packages/databases.scm (wiredtiger)[arguments]: Add --enable-snappy to
  #:configure-flags.
  [inputs]: Add snappy.

gnu: fish: Update to 2.7.1.

* gnu/packages/shells.scm (fish): Update to 2.7.1.

gnu: python-pillow: Update to 4.3.0.

* gnu/packages/python.scm (python-pillow): Update to 4.3.0.
[propagated-inputs]: Add python-olefile.
* gnu/packages/patches/python-pillow-freetype-2.7-test-failure.patch:
Delete file.
* gnu/local.mk (dist_patch_DATA): Remove it.

Signed-off-by: Kei Kebreau <kkebreau@posteo.net>

gnu: Add python-olefile.

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

gnu: mariadb: Update to 10.1.29.

* gnu/packages/databases.scm (mariadb): Update to 10.1.29.

file-systems: Move %control-groups from %base-file-systems to
%elogind-file-systems.

* gnu/system/file-systems.scm (%base-file-systems): Move %control-groups from
here, to ...
(%elogind-file-systems): ... here.

file-systems: Do not mount hugetlb cgroup filesystem.

On ARM32 without LPAE support, hugetlb control group is not supported.
As it is not needed by elogind, remove it for all platforms.

* gnu/system/file-systems.scm (%control-groups): Remove hugetlb from control
  groups platforms.

gnu: Update r-mutationalpatterns to 1.4.2.

* gnu/packages/bioinformatics.scm (r-mutationalpatterns): Update to 1.4.2.

gnu: mutter: Add xorg-xserver-xwayland input.

* gnu/packages/gnome.scm (mutter)[inputs]: Add xorg-server-xwayland.
[arguments]: Add '--with-xwayland-path' to #:configure-flags.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

guix system: Check mapped devices upon 'init' and 'reconfigure'.

* guix/scripts/system.scm (check-mapped-devices): New procedure.
(perform-action): Add call to 'check-mapped-devices'.

mapped-devices: 'luks-device-mapping' checks its source device.

* gnu/system/mapped-devices.scm (check-luks-device): New procedure.
(luks-device-mapping)[check]: New field.

mapped-devices: Add 'location' and 'check' fields.

* gnu/system/mapped-devices.scm (<mapped-device>)[location]: New field.
(<mapped-device-type>)[check]: New field.

gnu: Add python-activepapers.

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

Co-authored-by: Ludovic Courtès <ludovic.courtes@inria.fr>

services: urandom-seed: Depend on udev.

Suggested by Leo Famulari <leo@famulari.name>.

* gnu/services/base.scm (urandom-seed-shepherd-service): Add 'udev' to
'requirement'.

services: urandom-seed: Deprecate the 'urandom-seed-service' procedure.

* gnu/services/base.scm (urandom-seed-service-type)[default-value]: New
field.
(urandom-seed-service): Mark as deprecated.
(%base-services): Use URANDOM-SEED-SERVICE-TYPE directly.
* gnu/services/base.scm (%base-services):
* doc/guix.texi (Base Services): Document 'urandom-seed-service-type'
instead of 'urandom-seed-service'.

services: urandom-seed: Become a dependency of 'user-processes'.

This ensures that 'urandom-seed' is started before programs that rely on
sources of randomness.

Fixes <https://bugs.gnu.org/29773>.
Reported by Leo Famulari <leo@famulari.name>.

* gnu/services/base.scm (urandom-seed-shepherd-service): Change
'requirement' to (file-systems).
(urandom-seed-service-type): Extend USER-PROCESSES-SERVICE-TYPE.

services: 'user-processes-service-type' can now be extended.

* gnu/services/base.scm (user-processes-shepherd-service): New
procedure, taken from former 'user-processes-service-type'.  Add
REQUIREMENTS argument; remove GRACE-DELAY argument.
(user-processes-service-type): Redefine in terms of 'service-type'.
(user-processes-service): Remove.
(file-system-service-type): Extend USER-PROCESSES-SERVICE-TYPE.
* gnu/system.scm (essential-services): Use USER-PROCESSES-SERVICE-TYPE
directly.

doc: Document fixed-output derivations.

* doc/guix.texi (Derivations): Add paragraph on fixed-output
derivations.

system: examples: Add missing initrd to beaglebone-black.tmpl.

* gnu/system/examples/beaglebone-black.tmpl (operating-system): Add the
  initrd with "omap_hsmmc" as an extra-module.

gnu: Add meandmyshadow.

* gnu/packages/games.scm (meandmyshadow): New variable.