gnu: Add scmutils.

* gnu/packages/scheme.scm (scmutils): New variable.

gnu: Add ruby-bio-logger.

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

download: Only show hours in the elapsed time if necessary.

* guix/build/download.scm
  (seconds->string): Conditionally include hours in timestamp.

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

gnu: guile: Add guile-next

* gnu/packages/guile.scm (guile-next): New variable.
* gnu/packages/guile.scm (guile-for-guile-emacs):
  Adjust to inherit from guile-next rather than guile-2.0

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

gnu: Add emacs-typo.

* gnu/packages/emacs.scm (typo): New variable.

gnu: Add emacs-butler.

* gnu/packages/emacs.scm (butler): New variable.

gnu: Add emacs-deferred.

* gnu/packages/emacs.scm (emacs-deferred): New variable.

gnu: Add ruby-cucumber-core.

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

substitute: Improve readability of download progress report.

* guix/build/download.scm
  (string-pad-middle, store-url-abbreviation, store-path-abbreviation):
  New procedures.
  (progress-proc): Add #:abbreviation parameter and use it.  Generate a
  better indeterminate progress string.
* guix/scripts/substitute.scm (assert-valid-narinfo): Add newlines to output.
  (process-substitution): Use byte-count->string and store-path-abbreviation.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

gnu: Add mafft.

* gnu/packages/bioinformatics.scm (mafft): New variable.

gnu: Add keepassx.

* gnu/packages/password-utils.scm (keepassx): New variable.

gnu: Add python-requests-mock.

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

gnu: Add python-webob.

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

gnu: Add python-oslo.context.

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

gnu: Add python-oslo.serialization.

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

gnu: sfarklib: Update to 2.24.

* gnu/packages/compression.scm (sfarklib): Update to 2.24.

gnu: Add ruby-log4r.

* gnu/packages/ruby.scm (ruby-log4r): New variable.

gnu: Add r-dbi.

* gnu/packages/statistics.scm (r-dbi): New variable.

nls: Add "TRANSLATORS:" comment about Texinfo.

* gnu/packages/abiword.scm: Add comment above 'description'.

doc: Add guidelines for synopses and descriptions.

* doc/guix.texi (Synopses and Descriptions): New node.
* doc/contributing.texi (Submitting Patches): Add item that
  cross-references it.