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".

gnu: bootstrap: Add the location of ld.so on arm64.

* gnu/packages/bootstrap.scm (glibc-dynamic-linker): Add the dynamic
  linker for aarch64-linux.

doc: Mention --localstatedir for when building from Git.

Reported by Hartmut Goebel <h.goebel@crazy-compilers.com>.

* doc/contributing.texi (Building from Git): Mention --localstatedir.

doc: Fix typos.

* doc/guix.texi (Hardware Considerations): Fix typos.

syscalls: 'terminal-columns' ignores non-file ports.

* guix/build/syscalls.scm (terminal-columns): Call
'terminal-window-size' only when PORT is a file port.
* tests/syscalls.scm ("terminal-columns non-file port"): New test.

gnu: Add tcc-wrapper.

* gnu/packages/c.scm (tcc-wrapper): New variable.

gnu: Add tcc.

* gnu/packages/c.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.

doc: Remove mention of GNU release freshness checks.

* doc/guix.texi (Invoking guix package): Remove paragraph about
automatic check for latest GNU releases, which was removed in
6caa4dfa37e9b87336908e188500c14b402a0090.

gnu: Add Beast.

* gnu/packages/music.scm (beast): New variable.

gnu: Add rapicorn.

* gnu/packages/graphics.scm (rapicorn): New variable.

gnu: Add libpng-1.2.

* gnu/packages/image.scm (libpng-1.2): New variable.