gnu: libxml2: Add fixes for CVE-2015-{1819,7941,7942,8035} and other bugs.

* gnu/packages/patches/libxml2-CVE-2015-1819.patch,
  gnu/packages/patches/libxml2-CVE-2015-7941-pt1.patch,
  gnu/packages/patches/libxml2-CVE-2015-7941-pt2.patch,
  gnu/packages/patches/libxml2-CVE-2015-7942-pt1.patch,
  gnu/packages/patches/libxml2-CVE-2015-7942-pt2.patch,
  gnu/packages/patches/libxml2-CVE-2015-8035.patch,
  gnu/packages/patches/libxml2-bug-737840.patch,
  gnu/packages/patches/libxml2-bug-738805.patch,
  gnu/packages/patches/libxml2-bug-746048.patch,
  gnu/packages/patches/libxml2-bug-747437.patch,
  gnu/packages/patches/libxml2-bug-751603.patch,
  gnu/packages/patches/libxml2-bug-751631.patch,
  gnu/packages/patches/libxml2-bug-754946.patch,
  gnu/packages/patches/libxml2-bug-754947.patch,
  gnu/packages/patches/libxml2-bug-755857.patch,
  gnu/packages/patches/libxml2-fix-catalog-corruption.patch,
  gnu/packages/patches/libxml2-id-attrs-in-xmlSetTreeDoc.patch,
  gnu/packages/patches/libxml2-node-sort-order-pt1.patch,
  gnu/packages/patches/libxml2-node-sort-order-pt2.patch: New files.
* gnu-system.am (dist_patch_DATA): Add them.
* gnu/packages/xml.scm (libxml2)[source]: Add patches.

gnu: libpng: Update to 1.5.24 [fixes CVE-2015-8126].

* gnu/packages/image.scm (libpng): Update to 1.5.24.

Revert "gnu: libpng: Use 1.5.24 as a replacement [fixes CVE-2015-8126]."

This reverts commit 1b076e630f4a7245d14634b047e1d1a91ee2659e.

services: Export udev-configuration procedures.

* gnu/services/base.scm (udev-configuration, udev-configuration?,
  udev-configuration-rules): Export.

gnu: weechat: Fix patching of assignments to 'python2_bin'.

Fixes a regression introduced in a9346fa.

* gnu/packages/weechat.scm (weechat)[arguments]: Make sure PYTHON2_BIN
  can be freed with 'free'.

gnu: weechat: Encode as UTF-8.

* gnu/packages/weechat.scm: Reencode as UTF-8.

gnu: weechat: Record the absolute file name of 'python'.

Fixes <http://bugs.gnu.org/21879>.
Reported by Luis Felipe López Acevedo <felipe.lopez@openmailbox.org>.

* gnu/packages/weechat.scm (weechat)[arguments]: Add
  'set-python-file-name' phase.

gnu: weechat: Use 'modify-phases'.

* gnu/packages/weechat.scm (weechat)[arguments]: Use 'modify-phases'.
  Remove 'fix-file' phase.

gnu: python-tornado: Use the preferred home-page.

* gnu/packages/python.scm (python-tornado)[home-page]: Use the preferred
  one.

gnu: python-cryptography: Update to 1.0.2.

* gnu/packages/python.scm (python-cryptography): Update to 1.0.2.

gnu: python-cryptography-vectors: Update to 1.0.2.

* gnu/packages/python.scm (python-cryptography-vectors): Update to 1.0.2.

gnu: zynaddsubfx: Update to 2.5.2.

* gnu/packages/music.scm (zynaddsubfx): Update to 2.5.2.

gnu: Add python-pystache.

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

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

Revert "gnu: wget: Update to 1.17."

This reverts commit 4ca02340691624316330619fc6fec5a5e68e00b7.

gnu: Add network-manager-applet.

* gnu/packages/gnome.scm (network-manager-applet): New variable.

gnu: Add network-manager.

* gnu/packages/gnome.scm (%network-manager-glib-duplicate-test-patch)
(network-manager): New variables.

gnu: youtube-dl: Update to 2015.11.15.

* gnu/packages/video.scm (youtube-dl): Update to 2015.11.15.

Thank Chris.

ftp-client: Restrict to TCP/IP connections.

Fixes <http://bugs.gnu.org/21925>.
Regression introduced in 279ec1d.
Reported by Chris Marusich <cmmarusich@gmail.com>.

* guix/ftp-client.scm (ftp-open): Restrict sockets to
  SOCK_STREAM/IPPROTO_IP.

gnu: Add Scribus.

* gnu/packages/scribus.scm: New file
* gnu/packages/patches/scribus-qobject.scm: New file.
* gnu-system.am (GNU_SYSTEM_MODULES, dist_patch_DATA): Add them.