services: udev: Improve synchronization when starting.

* gnu/services/base.scm (udev-service)[start]: Add 'wait-for-udevd', and
  call it before running 'udevadm trigger'.  Pass --action=add to
  'udevadm trigger'.  Call 'udevadm settle' after 'udevadm trigger'.

services: xorg: Remove optional sections from xorg.conf.

* gnu/services/xorg.scm (xorg-start-command)[xserver.conf]: Remove
  sections "Monitor", "InputClass", "ServerLayout", "Device", and
  "Screen".

services: xorg: Require 'udev'.

* gnu/services/xorg.scm: Add 'udev' to the 'requirement' field.

services: xorg: Add drivers to the default search path.

* gnu/services/xorg.scm (xorg-start-command)[xserver.conf]: Add
  'ModulePath' entries for xf86-video-{fbdev,cirrus,intel,mach64,nv} and
  xf86-input-{synaptics,vmmouse}.

services: xorg: Fix typo in font path.

* gnu/services/xorg.scm (xorg-start-command)[xserver.conf]: Fix typo in
  font path.

gnu: Add sipwitch and dependent packages

* gnu-system.am (GNU_SYSTEM_MODULES): Add new file.
* gnu/packages/telephony.scm: New file.

gnu: Add conkeror.

* gnu-system.am (GNU_SYSTEM_MODULES): Add new package.
* gnu/packages/conkeror.scm: New file.

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

gnu: tor: Upgrade to 0.2.4.22.

* gnu/packages/tor.scm (tor): Upgrade to 0.2.4.22.

services: Update to use the dmd 0.2 API.

* gnu/services/avahi.scm (avahi-service)[start]: Wrap command in a
  list.
* gnu/services/dbus.scm (dbus-service)[start]: Likewise.
* gnu/services/ssh.scm (lsh-service): Likewise.
* gnu/services/base.scm (mingetty-service)[start]: Likewise.
  (nscd-service)[start]: Likewise.
  (syslog-service)[start]: Likewise.
  (guix-service)[start]: Likewise.
  (udev-service)[start]: Use 'exec-command' instead of 'execl'.
* gnu/services/xorg.scm (slim-service)[start]: Likewise, and use
  #:environment-variables.

gnu: dmd: Update to 0.2.

* gnu/packages/admin.scm (dmd): Update to 0.2; remove 'patches'.
* gnu/packages/patches/dmd-getpw.patch,
  gnu/packages/patches/dmd-tests-longer-sleeps.patch: Remove.
* gnu-system.am (dist_patch_DATA): Adjust accordingly.

gnu: linux-libre: Use the GNU + Freedo boot logo.

* gnu/packages/linux.scm (%boot-logo-patch): New variable.
  (linux-libre)[build-phase]: Apply it.
  [native-inputs]: Add it.

gnu: bitlbee: Upgrade to 3.2.2.

* gnu/packages/messaging.scm (bitlbee): Upgrade to 3.2.2.  Remove patches.
  Use 'libotr' instead of 'libotr-3'.
* gnu/packages/patches/bitlbee-fix-tests.patch: Remove file.
* gnu/packages/patches/bitlbee-memset-fix.patch: Remove file.
* gnu-system.am (dist_patch_DATA): Remove patches.

gnu: gnupg: Update to 2.0.25 and 1.4.18.

* gnu/packages/gnupg.scm (gnupg): Update to 2.0.25.
  (gnupg-1): Update to 1.4.18.

gnu: Add maxima.

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

gnu: Add gcl.

* gnu-system.am (GNU_SYSTEM_MODULES): Add new package.
* gnu/packages/lisp.scm: New file.

vm: Enable QEMU support in the freestanding VM image.

* gnu/system/vm.scm (system-qemu-image): Add 'initrd' field.

gnu: Avoid circular dependency among modules.

Reported by Alex Kost <alezost@gmail.com>.

* gnu/packages/python.scm: Don't use #:select for (gnu packages zip).

gnu: Add gegl and gimp

* gnu/packages/gimp.scm (gegl, gimp): New variables.

gnu: Add youtube-dl.

* gnu/packages/video.scm (youtube-dl): New variable.

gnu: pdf: Add PoDoFo.

* gnu/packages/pdf.scm (podofo): New variable.