gnu: Add gerbv.

* gnu/packages/engineering.scm (gerbv): New variable.

gnu: Add po4a.

* gnu/packages/gettext.scm (po4a): New variable.

gnu: Add TeX Gyre fonts.

* gnu/packages/fonts.scm (font-tex-gyre): New variable.

gnu: Add sassc.

* gnu/packages/web.scm (sassc): New variable.

gnu: Add python-oslotest

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

gnu: Add python-os-client-config

* gnu/packages/openstack.scm (python-os-client-config,
  python2-os-client-config): New variables.

gnu: Add python-mox3.

* gnu/packages/openstack.scm (python-mox3, python2-mox3): New variables.

gnu: Add python-pbr.

* gnu/packages/openstack.scm: New file.
* gnu-system.am: Add it.

gnu: add python-appdirs.

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

gnu: guile-ssh: Update to 0.8.0.

* gnu/packages/ssh.scm (guile-ssh): Update to 0.8.0.
  [inputs]: Use LIBGCRYPT instead of LIBGCRYPT-1.5.

gnu: libssh: Update to 0.6.5.

* gnu/packages/ssh.scm (libssh): Update to 0.6.5.
  [source]: Remove 'patches'.
  [inputs]: Use LIBGCRYPT instead of LIBGCRYPT-1.5.

gnu: Add emacs-flycheck.

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

gnu: Add emacs-let-alist.

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

gnu: Add Guile-Present.

* gnu/packages/gtk.scm (guile-present): New variable.

gnu: Add Guile-RSVG.

* gnu/packages/gtk.scm (guile-rsvg): New variable.
* gnu/packages/patches/guile-rsvg-pkgconfig.patch: New file.
* gnu-system.am (dist_patch_DATA): Add it.

gnu: Add frescobaldi.

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

gnu: Add python-ly.

* gnu/packages/python.scm (python-ly): New variable.

gnu: Add python-poppler-qt4.

* gnu/packages/pdf.scm (python-poppler-qt4): New variable.

gnu: Add poppler-qt4.

* gnu/packages/pdf.scm (poppler-qt4): New variable.

gnu: Add ruby-thor.

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