services: Statically report duplicate dmd service identifiers.

Reported by 白い熊 @相撲道 <guix-devel_gnu.org@sumou.com>
at <http://lists.gnu.org/archive/html/guix-devel/2015-03/msg00264.html>.

* gnu/services/dmd.scm (assert-no-duplicates): New procedure.
  (dmd-configuration-file): Use it.
* po/guix/POTFILES.in: Add gnu/services/dmd.scm.
* tests/guix-system.sh (errorfile): Add test.

nls: Update 'eo' translation.

nls: Update 'vi' translation.

nls: Add a few more package modules for translation.

* po/packages/POTFILES.in: List a few more files.

Merge branch 'master' into core-updates

nls: Update 'eo' translation.

Merge branch 'master' into core-updates

nls: Add French translation for packages.

Merge branch 'master' into 'core-updates'.

nls: Add French translation.

nls: Update 'eo' translation.

nls: Update Hungarian translation.

nls: Add Hungarian translation.

* po/packages/hu.po: New file.
* po/packages/LINGUAS: Add it.

system: Build system-wide locale definitions.

* gnu/system/locale.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES): Add it.
* gnu/system.scm (<operating-system>)[locale]: Change the default to
  "en_US.utf8".
  (operating-system-locale-directory): New procecure.
  (operating-system-derivation): Use it.
* doc/guix.texi (Using the Configuration System): Change example locale
  to "fr_FR.utf8".
  (operating-system Reference): Add xref to "Locales".  Document
  'locale-definitions'.
  (Locales): New section.
* po/guix/POTFILES.in: Add gnu/system.scm.

nls: Update 'vi' translation.

nls: Update 'de' translation.

nls: Add a few more package modules for translation.

* po/packages/POTFILES.in: List a few more files.

nls: Recognize 'N_' as equivalent to 'ngettext'.

This fixes i18n of plural messages.

* po/guix/Makevars (XGETTEXT_OPTIONS): Change 'N_' to 'N_:1,2'.

Merge branch 'master' into core-updates

Conflicts:
	gnu-system.am

nls: Update 'sr' translation.