doc: merge docs/ dir → doc/

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

docs/var-log/README.in

@@ -1,26 +0,0 @@
-You are looking for the traditional text log files in @VARLOGDIR@, and
-they are gone?
-
-Here's an explanation on what's going on:
-
-You are running a systemd-based OS where traditional syslog has been
-replaced with the Journal. The journal stores the same (and more)
-information as classic syslog. To make use of the journal and access
-the collected log data simply invoke "journalctl", which will output
-the logs in the identical text-based format the syslog files in
-@VARLOGDIR@ used to be. For further details, please refer to
-journalctl(1).
-
-Alternatively, consider installing one of the traditional syslog
-implementations available for your distribution, which will generate
-the classic log files for you. Syslog implementations such as
-syslog-ng or rsyslog may be installed side-by-side with the journal
-and will continue to function the way they always did.
-
-Thank you!
-
-Further reading:
-        man:journalctl(1)
-        man:systemd-journald.service(8)
-        man:journald.conf(5)
-        http://0pointer.de/blog/projects/the-journal.html

docs/var-log/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 : varlogdir)
-endif