uuid: 'uuid' macro supports more UUID types.

* gnu/system/uuid.scm (string->uuid): Turn 'type' into an optional
argument.
(uuid): Add clauses to allow for an optional 'type' parameter.

system: Serialize the UUID type in the "parameters" file.

* gnu/system.scm (read-boot-parameters)[device->sexp]: New procedure.
Use it for 'root-device' and 'store-device'.
(device->sexp): Serialize the UUID type in addition to its bytevector.

system: Introduce a disjoint UUID type.

Conceptually a UUID is just a bytevector.  However, there's software out
there such as GRUB that relies on the string representation of different
UUID types (e.g., the string representation of DCE UUIDs differs from
that of ISO-9660 UUIDs, even if they are actually bytevectors of the
same length).  This new <uuid> record type allows us to preserve
information about the type of UUID so we can eventually convert it to a
string using the right representation.

* gnu/system/uuid.scm (<uuid>): New record type.
(bytevector->uuid): New procedure.
(uuid): Return calls to 'make-uuid'.
(uuid->string): Rewrite using 'match-lambda*' to accept a single 'uuid?'
argument.
* gnu/bootloader/grub.scm (grub-root-search): Check for 'uuid?' instead
of 'bytevector?'.
* gnu/system.scm (bootable-kernel-arguments): Check whether ROOT-DEVICE
is 'uuid?'.
(read-boot-parameters): Use 'bytevector->uuid' when the
store device is a bytevector.
(read-boot-parameters-file): Check for 'uuid?' instead of 'bytevector?'.
(device->sexp): New procedure.
(operating-system-boot-parameters-file): Use it for 'root-device' and
'store'.
(operating-system-bootcfg): Remove conditional in definition of
'root-device'.
* gnu/system/file-systems.scm (file-system->spec): Check for 'uuid?' on
DEVICE and take its bytevector.
* gnu/system/mapped-devices.scm (open-luks-device): Likewise.
* gnu/system/vm.scm (iso9660-image): Call 'uuid-bytevector' for the
 #:volume-uuid argument.

services: file-system: Use 'file-system->spec'.

* gnu/services/base.scm (file-system-shepherd-service): Use
'file-system->spec' instead of in-line code.

file-systems: Introduce (gnu system uuid).

* gnu/build/file-systems.scm (sub-bytevector)
(latin1->string, %fat32-endianness, fat32-uuid->string)
(%iso9660-uuid-rx, string->iso9660-uuid)
(iso9660-uuid->string, %network-byte-order)
(dce-uuid->string, %uuid-rx, string->dce-uuid)
(string->ext2-uuid, string->ext3-uuid, string->ext4-uuid)
(vhashq, %uuid-parsers, %uuid-printers, string->uuid)
(uuid->string): Move to...
* gnu/system/uuid.scm: ... here.  New file.
* gnu/system/file-systems.scm (uuid): Move to the above file.
* gnu/system/vm.scm: Adjust accordingly.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add uuid.scm.

services: base: Import the closure of (gnu build file-systems).

* gnu/services/base.scm (file-system-shepherd-service): Use
'source-module-closure' in the 'with-imported-modules' form.

file-systems: Add UUID type dictionaries.

* gnu/build/file-systems.scm (uuid->string): Rename to...
(dce-uuid->string): ... this.
(string->uuid): Rename to...
(string->dce-uuid): ... this.
(vhashq): New macro.
(%uuid-parsers, %uuid-printers): New variables.
(uuid->string, string->uuid): New procedures.

vm: Allow partitions to be initialized with a given UUID.

* gnu/build/vm.scm (<partition>)[uuid]: New field.
(create-ext-file-system): Add #:uuid and honor it.
(create-fat-file-system): Add #:uuid.
(format-partition): Add #:uuid and honor it.
(initialize-partition): Honor the 'uuid' field of PARTITION.

gnu: mpg123: Update to 1.25.6 [fixes CVE-2017-12797].

* gnu/packages/mp3.scm (mpg123): Update to 1.25.6.

gnu: libchamplain: Update to 0.12.16.

* gnu/packages/gnome.scm (libchamplain): Update to 0.12.16.

gnu: gnome-online-accounts: Update to 3.24.3.

* gnu/packages/gnome.scm (gnome-online-accounts): Update to 3.24.3.

gnu: emacs: Patch message-mode enriched text translation [security fix].

* gnu/packages/patches/emacs-unsafe-enriched-mode-translations.patch:
New file.
* gnu/packages/emacs.scm (emacs)[source](patches): Add it.
* gnu/local.mk (dist_patch_DATA): Add it.

gnu: nyacc: Update to 0.82.0.

* gnu/packages/mes.scm (nyacc): Update to 0.82.0.

gnu: ruby-activesupport: Update to 5.1.4.

* gnu/packages/ruby.scm (ruby-activesupport): Update to 5.1.4.

gnu: icedtea-8: Install the nss.cfg file to JRE.

Before this, accessing HTTPS will throw an exception about 'nss.cfg' could not
be found.

* gnu/packages/java.scm (icedtea-8)[arguments]: Copy 'nss.cfg' from JDK into
JRE in the install phase.

gnu: gdb: Update to 8.0.1.

* gnu/packages/gdb.scm (gdb): Update to 8.0.1.

download: Adjust main ftp.gnu.org mirror.

* guix/download.scm (%mirrors): Add missing "/gnu" in first mirror,
although that mirror would work even without it.  Use https instead of
http.

gnu-maintenance: Return all the latest tarballs, not just one.

* guix/gnu-maintenance.scm (latest-gnu-release): Return a list of
matching tarballs instead of just the first one.  This gives us .tar.gz,
.tar.xz, etc.

gnu-maintenance: Correctly compare versions.

* guix/gnu-maintenance.scm (latest-gnu-release): Add calls to
'sans-extension'.  This fixes version comparison, which could be fooled
with the ".tar.gz" extension.

gnu: guix: Update snapshot.

* gnu/packages/package-management.scm (guix): Update to a9468b4.