build: Improve information density and appearance of download progress output.

* guix/build/download.scm (seconds->string): New function.
  (byte-count->string): New function.
  (progress-bar): New function.
  (throughput->string): Remove function.
  (progress-proc): Display base file name, elapsed time, and progress bar.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

ui: Add package-description-string.

Provide support for Texinfo's markup in package description.

* guix/ui.scm (%text-width): New parameter.
  (texi->plain-text): New variable.
  (package->recutils): Use them.
  (package-description-string): New variable.
* emacs/guix-main.scm (%package-param-alist): Use it.
* gnu/packages/perl.scm (perl-devel-globaldestruction)
  (perl-devel-lexalias, perl-exporter-lite): Adapt to Texinfo's markup.
* gnu/packages/python.scm (python2-empy): Likewise.

gnu: Add oslo.i18n.

* gnu/packages/openstack.scm (python-oslo.i18n, python2-oslo.i18n): New
  variables.

gnu: python-testtools: fix propagated inputs.

* gnu/packages/python.scm (python-testools): turn python-fixtures and
  python-testtools into propagated inputs.

gnu: pbr: Update to 1.6.0

* gnu/packages/openstack.scm (python-pbr): Update to 1.6.0.

gnu: Add ruby-rack.

* gnu/packages/ruby.scm (ruby-rack): New variable.

build: container: Use the same clone flags as fork(3).

The intent is to make 'clone' behave a lot more like 'primitive-fork', which
calls clone(2) with SIGCHLD, CLONE_CHILD_CLEARTID, and CLONE_CHILD_SETTID
flags.  Notably, running 'clone' at the REPL without these flags would break
the REPL beyond repair.

* guix/build/syscalls.scm (CLONE_CHILD_CLEARTID, CLONE_CHILD_SETTID): New
  variables.
* gnu/build/linux-container.scm (namespaces->bit-mask): Add
  CLONE_CHILD_CLEARTID and CLONE_CHILD_SETTID to bit mask.

build: container: Setup /dev/console.

* gnu/build/linux-container.scm (mount-file-systems): Bind mount the
  controlling terminal as /dev/console.

gnu: Add ruby-byebug.

* gnu/packages/ruby.scm (ruby-byebug): New variable.

gnu: Add ruby-pg.

* gnu/packages/ruby.scm (ruby-pg): New variable.

build: ruby: Avoid long build directory names.

Having the hash of the source gem in the source directory file name proved to
be problematic when running the test suite for the 'pg' gem that creates
UNIX-domain sockets in the source directory and exceeded the 108 character
limit on GNU/Linux systems.

* guix/build/ruby-build-system.scm (unpack): Rename unpacked gem directory to
  "gem".

gnu: Add enblend-enfuse.

* gnu/packages/photo.scm (enblend-enfuse): New variable.

gnu: calibre: Update to 2.37.1.

* gnu/packages/ebook.scm (calibre): Update to 2.37.1.

gnu: Add FLANN.

* gnu/packages/maths.scm (flann): New variable.

gnu: youtube-dl: Update to 2015.09.03.

* gnu/packages/video.scm (youtube-dl): Update to 2015.09.03.

gnu: Add libpano13.

* gnu/packages/photo.scm (libpano13): New variable.

ui: Change 'P_' to return the empty string when passed the empty string.

Reported by Mathieu Lirzin <mathieu.lirzin@etu.u-bordeaux.fr>
at <https://lists.gnu.org/archive/html/guix-devel/2015-09/msg00111.html>.

* guix/ui.scm (P_): Check whether MSGID is empty, and return it if it is.

Update copyright information in (gnu packages ruby).

gnu: Add ruby-ox.

* gnu/packages/ruby.scm (ruby-ox): New variable.

gnu: Add ruby-activesupport.

* gnu/packages/ruby.scm (ruby-activesupport): New variable.