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.

gnu: emacs-ivy: Install documentation.

* gnu/packages/emacs.scm (emacs-ivy)[arguments]: Add phase "install-doc".
[native-inputs]: Add texinfo.

gnu: emacs-ivy: Update to 0.10.0.

* gnu/packages/emacs.scm (emacs-ivy): Update to 0.10.0.

gnu: Add plzip.

* gnu/packages/compression.scm (plzip): New public variable.

gnu: Add lzlib.

* gnu/packages/compression.scm (lzlib): New public variable.

gnu: Add clzip.

* gnu/packages/compression.scm (clzip): New public variable.

gnu: Add lunzip.

* gnu/packages/compression.scm (lunzip): New public variable.

gnu: Add hungrycat.

* gnu/packages/admin.scm (hungrycat): New public variable.

gnu: zstd: Use default ‘check’ target.

* gnu/packages/compression.scm (zstd)[arguments]: Don't set #:test-target.