services: Move 'device-mapping-service' to (gnu system mapped-devices).

* gnu/services/base.scm (device-mapping-service-type)
(device-mapping-service): Move to...
* gnu/system/mapped-devices.scm (device-mapping-service-type):
(device-mapping-service): ... here.  New variables.

system: Move 'luks-device-mapping' to (gnu system mapped-devices).

* gnu/system.scm (open-luks-device, close-luks-device)
(luks-device-mapping): Move to...
* gnu/system/mapped-devices.scm: ... here.  New file.

system: Add (gnu system mapped-devices).

* gnu/system/file-systems.scm (<mapped-device>, <mapped-device-type>):
Move to...
* gnu/system/mapped-devices.scm: ... here.  New file.
* gnu/system.scm, gnu/services/base.scm,
gnu/system/linux-initrd.scm: Use it.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.
* gnu.scm (%public-modules): Add it.

gnu: Add python-pyusb.

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

gnu: khard: Update to 0.9.0.

* gnu/packages/mail.scm (khard): Update to 0.9.0.

gnu: python-vobject: Update to 0.9.2.

* gnu/packages/python.scm (python-vobject, python2-vobject): Update to 0.9.2.

gnu: openssh: Fix CVE-2015-8325.

* gnu/packages/patches/openssh-CVE-2015-8325.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.
* gnu/packages/ssh.scm (openssh): Use it.

gnu: Add recordmydesktop.

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

install: Use 'beta' instead of 'alpha'.

Suggested by Jelle Licht <jlicht@fsfe.org>.

* gnu/system/install.scm (installation-services): Say 'beta' instead of
'alpha' and make the warning less scary.

gnu: python-pandas: Fix test failures.

* gnu/packages/patches/python-pandas-fix-tslib-test-failure.patch: New
  file.
* gnu-system.am (dist_patch_DATA): Register it.
* gnu/packages/python.scm (python-pandas)[source]: Add patch.

gnu: icedtea-7: Update to 2.6.5.

* gnu/packages/java.scm (icedtea-7): Update to 2.6.5.
[inputs]: Add libxcomposite.

services: 'console-keymap-service' takes multiple files.

* gnu/services/base.scm (console-keymap-service-type): Type procedure
takes a list of files instead of a single file.
(console-keymap-service): Take 'files' as rest arguments.
* doc/guix.texi (Base Services): Improve documentation of
'console-keymap-service'.

gnu: kbd: Update to 2.0.3.

* gnu/packages/linux.scm (kbd): Update to 2.0.3.

gnu: kbd: Use 'modify-phases'.

* gnu/packages/linux.scm (kbd)[arguments]: Use 'modify-phases'.

file-systems: Add 'find-partition-by-luks-uuid'.

* gnu/build/file-systems.scm (%luks-endianness, %luks-header-size): New
macros.
(%luks-magic): New variable.
(sub-bytevector, read-luks-header, luks-header-uuid): New procedures.
(partition-predicate): Add 'read' parameter; wrap it with 'ENOENT-safe'.
Use it instead of 'read-ext2-superblock*'.
(read-ext2-superblock*): Remove.
(partition-label-predicate, partition-uuid-predicate): Pass
'read-ext2-superblock' as the first argument.
(partition-luks-uuid-predicate): New variable.
(find-partition-by-luks-uuid): New procedure.

file-systems: Separate ENOENT catching from ext2 superblock reads.

* gnu/build/file-systems.scm (ENOENT-safe): New procedure.
(read-ext2-superblock*): Rewrite in terms of it.

doc: Update 'skeletons' field documentation.

* doc/guix.texi (operating-system Reference): Update documentation of
'skeletons' as a followup to e79467f63a06811ba5dd8c8b0cc79553c5dd4e3a.

doc: Use new PACKAGE@VERSION syntax in example.

* doc/guix.texi (Using the Configuration System): Use PACKAGE@VERSION
syntax.

gnu: Add marst.

* gnu/packages/marst.scm: New file.
* gnu-system.am: Add it.

gnu: linux: Add case for arm64.

* gnu/packages/linux.scm (system->linux-architecture): Add
  "aarch64".