Drop support for sysvinit scripts

As announced by a few releases now, finally drop support for
sysvinit scripts.
Keep rc-local generator for now, as it's really a distinct
feature even though from the same era.

docs/DISTRO_PORTING.md

@@ -13,8 +13,6 @@ You need to make the follow changes to adapt systemd to your distribution:
 
 1. Find the right configure parameters for:
 
-   * `-Dsysvinit-path=`
-   * `-Dsysvrcnd-path=`
    * `-Drc-local=`
    * `-Dloadkeys-path=`
    * `-Dsetfont-path=`

docs/ENVIRONMENT.md

@@ -449,14 +449,6 @@ All tools:
   as a child process by another tool, such as package managers running it in a
   postinstall script.
 
-`systemd-sysv-generator`:
-
-* `$SYSTEMD_SYSVINIT_PATH` — Controls where `systemd-sysv-generator` looks for
-  SysV init scripts.
-
-* `$SYSTEMD_SYSVRCND_PATH` — Controls where `systemd-sysv-generator` looks for
-  SysV init script runlevel link farms.
-
 systemd tests:
 
 * `$SYSTEMD_TEST_DATA` — override the location of test data. This is useful if

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-been replaced by native systemd services files.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)
-        https://0pointer.de/blog/projects/systemd-for-admins-3.html
-        https://systemd.io/INCOMPATIBILITIES

docs/sysvinit/meson.build

@@ -1,8 +0,0 @@
-# SPDX-License-Identifier: LGPL-2.1-or-later
-
-custom_target(
-        input : 'README.in',
-        output : 'README',
-        command : [jinja2_cmdline, '@INPUT@', '@OUTPUT@'],
-        install : conf.get('HAVE_SYSV_COMPAT') == 1,
-        install_dir : sysvinit_path)