doc: merge docs/ dir → doc/

It's weird having two subdirs for documentation, let's unify this in
one.

docs/sysvinit/README.in

@@ -1,27 +0,0 @@
-You are looking for the traditional init scripts in @SYSTEM_SYSVINIT_PATH@,
-and they are gone?
-
-Here's an explanation on what's going on:
-
-You are running a systemd-based OS where traditional init scripts have
-been replaced by native systemd services files. Service files provide
-very similar functionality to init scripts. To make use of service
-files simply invoke "systemctl", which will output a list of all
-currently running services (and other units). Use "systemctl
-list-unit-files" to get a listing of all known unit files, including
-stopped, disabled and masked ones. Use "systemctl start
-foobar.service" and "systemctl stop foobar.service" to start or stop a
-service, respectively. For further details, please refer to
-systemctl(1).
-
-Note that traditional init scripts continue to function on a systemd
-system. An init script @SYSTEM_SYSVINIT_PATH@/foobar is implicitly mapped
-into a service unit foobar.service during system initialization.
-
-Thank you!
-
-Further reading:
-        man:systemctl(1)
-        man:systemd(1)
-        http://0pointer.de/blog/projects/systemd-for-admins-3.html
-        https://www.freedesktop.org/wiki/Software/systemd/Incompatibilities

docs/sysvinit/meson.build

@@ -1,26 +0,0 @@
-# SPDX-License-Identifier: LGPL-2.1+
-#
-# Copyright 2017 Zbigniew Jędrzejewski-Szmek
-#
-# systemd is free software; you can redistribute it and/or modify it
-# under the terms of the GNU Lesser General Public License as published by
-# the Free Software Foundation; either version 2.1 of the License, or
-# (at your option) any later version.
-#
-# systemd is distributed in the hope that it will be useful, but
-# WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-# Lesser General Public License for more details.
-#
-# You should have received a copy of the GNU Lesser General Public License
-# along with systemd; If not, see <http://www.gnu.org/licenses/>.
-
-file = configure_file(
-        input : 'README.in',
-        output : 'README',
-        configuration : substs)
-
-if conf.get('HAVE_SYSV_COMPAT') == 1
-        install_data(file,
-                     install_dir : sysvinit_path)
-endif