system: update checkout.

Submodule system 6b334d4..e6fa2fa:
> user/miscellanea: bash_rc: add find_newer() function.
> system/essential/verbatim-toplevel: netctl: update WLAN profiles.
> system/essential/archlinux: makepkg.conf.*: update OPTIONS.
> system/essential/verbatim-toplevel: netctl, router: minor fixes to self-
hosted network configuration.
> system/essential/verbatim-toplevel: bluetooth: update.
> system/essential/verbatim-toplevel: add lightdm-session: custom top-level
Xsession for LightDM.
> user/miscellanea: bash_rc: fix PS1 again.
> system/essential/verbatim-toplevel: netctl: update profiles.
> user/miscellanea: bash_rc: fix PS1.
> system/essential/verbatim-toplevel: netctl: update profiles.
> system/essential/verbatim-toplevel: netctl, router: move self-hosted WLAN
network definition to embedded configsection.
> system/essential: rip out hand-made infrastructure for pm-utils.
> configs/general: configs-common: /etc/default/grub: re-enable submenu
generation, enable hidden menu and shorten timeout.
> configs/general: rename common-systemd -> systemd-common.
> configs/general: common-systemd: delete some entries unneeded by default
(like hddtemp and lm_sensors).
> configs/desktop: rename desktop-systemd -> systemd-desktop.
> configs: split off KDE-related data into 'kde' group.
> configs/desktop: desktop-systemd: delete leftovers of ModemManager.
> configs: move general/common-serv-ssh to pool/own-serv-ssh.
> configs/desktop: rename desktop-systemd-pm-init -> systemd-pm-powersave.
> configs/desktop: desktop-samba: remove, samba is not installed by default.
> configs/critical: critical-ld: remove /usr/local/bin/ld kludge, not needed
anymore.
> configs/virtualbox: rename desktop-modules-vbox -> modules-vbox.
> configs/general: merge common-{assorted,mkinitcpio} -> configs-common.