This commit updates $license variable in all APKBUILDs to comply with
short names specified by SPDX version 3.0 [1] where possible. It was
done using find-and-replace method on substrings inside $license
variables.

Only license names were updated, not "expressions" specifying relation
between the licenses (e.g. "X and Y", "X or Y", "X and (Y or Z)") or
exceptions (e.g. "X with exceptions").

Many licenses have a version or multiple variants, e.g. MPL-2.0,
BSD-2-Clause, BSD-3-Clause. However, $license in many aports do not
contain license version or variant. Since there's no way how to infer
this information just from abuild, it were left without the variant
suffix or version, i.e. non SPDX compliant.

GNU licenses (AGPL, GFDL, GPL, LGPL) are especially complicated. They
exist in two variants: -only (formerly e.g. GPL-2.0) and -or-later
(formerly e.g. GPL-2.0+). We did not systematically noted distinguish
between these variants, so GPL-2.0, GPL2, GPLv2 etc. may mean
GPL-2.0-only or GPL-2.0-or-later. Thus GNU licenses without "+" (e.g.
GPL2+) were left without the variant suffix, i.e. non SPDX compliant.

Note: This commit just fixes format of the license names, no
verification has been done if the specified license information is
actually correct!

[1]: https://spdx.org/licenses/

Now all invocations have following order of arguments (if present):

    addgroup -S -g ... GROUP
    adduser -S -u ... -D -H -h ... -s ... -G ... -g ... USER

Following rules have been applied:
- script starts with shebang !#/bin/sh followed by blank line,
- script ends with exit 0 prepended by blank line,
- only stderr of adduser, addgroup or passwd is redirected to /dev/null,
- getent passwd/group instances has been removed,
- manual checking of file and group existence has been removed,
- `|| true` instances has been removed.

Comments and line wrapping have been preserved.

This way we can avoid ugly default:

    Linux user,,,

Groups and users created by packages shouldn't use high ids by default
(unless explicitly requested), to distinguish them from groups and users
created by administrators for humans.

Following 41 files lacked -S next to addgroup:
- community/sword/sword.pre-install
- main/amavisd-new/amavisd-new.pre-install
- main/chrony/chrony.pre-install
- main/cvechecker/cvechecker.pre-install
- main/dnsmasq/dnsmasq.pre-install
- main/freeradius/freeradius.pre-install
- main/gdnsd/gdnsd.pre-install
- main/haproxy/haproxy.pre-install
- main/haproxy/haproxy.pre-upgrade
- main/kamailio/kamailio.pre-install
- main/logcheck/logcheck.pre-install
- main/mlmmj/mlmmj.pre-install
- main/nrpe/nrpe.pre-install
- main/open-vm-tools/open-vm-tools.pre-install
- main/postgrey/postgrey.pre-install
- main/privoxy/privoxy.pre-install
- main/redis/redis.pre-install
- main/samba/winbind.pre-install
- main/sircbot/sircbot.pre-install
- main/smokeping/smokeping.pre-install
- main/squark/squark.post-install
- main/squid/squid.pre-install
- main/squid/squid.pre-upgrade
- main/subversion/subversion.pre-install
- main/trac/trac.pre-install
- main/vsftpd/vsftpd.pre-install
- main/zabbix/zabbix-agent.pre-install
- testing/3proxy/3proxy.pre-install
- testing/cluster-glue/cluster-glue.pre-install
- testing/elasticsearch/elasticsearch.pre-install
- testing/emby/emby.pre-install
- testing/gdnsd/gdnsd.pre-install
- testing/icinga2/icinga2.pre-install
- testing/lusca/lusca.pre-install
- testing/lusca/lusca.pre-upgrade
- testing/mongodb/mongodb.pre-install
- testing/openxcap/openxcap.pre-install
- testing/prosody/prosody.pre-install
- testing/rancid/rancid.pre-install
- testing/rutorrent/rutorrent.pre-install
- testing/zabbix/zabbix-agent.pre-install

Following 60 files lacked -S next to adduser:
- community/caddy/caddy.pre-install
- community/domoticz/domoticz.pre-install
- community/minetest/minetest-server.pre-install
- community/oscam/oscam.pre-install
- community/seafile/seafile-server.pre-install
- community/syncthing/syncthing.pre-install
- main/apache2/apache2.pre-install
- main/aports-build/aports-build.pre-install
- main/atheme-iris/atheme-iris.pre-install
- main/bind/bind.pre-install
- main/clamav/clamav-db.pre-install
- main/clamsmtp/clamsmtp.pre-install
- main/clamsmtp/clamsmtp.pre-upgrade
- main/coova-chilli/coova-chilli.pre-install
- main/cvechecker/cvechecker.pre-install
- main/dhcp/dhcp.pre-install
- main/distcc/distcc.pre-install
- main/djbdns/dnscache.pre-install
- main/djbdns/tinydns.pre-install
- main/dovecot/dovecot.pre-install
- main/ez-ipupdate/ez-ipupdate.pre-install
- main/fetchmail/fetchmail.pre-install
- main/freeswitch/freeswitch.pre-install
- main/gitolite/gitolite.pre-install
- main/gnats/gnats.pre-install
- main/gross/gross.pre-install
- main/icecast/icecast.pre-install
- main/kamailio/kamailio.pre-install
- main/lighttpd/lighttpd.pre-install
- main/mariadb/mariadb.pre-install
- main/memcached/memcached.pre-install
- main/ngircd/ngircd.pre-install
- main/nrpe/nrpe.pre-install
- main/openntpd/openntpd.pre-install
- main/postgrey/postgrey.pre-install
- main/snort/snort.pre-install
- main/squid/squid.pre-install
- main/squid/squid.pre-upgrade
- main/subversion/subversion.pre-install
- main/trac/trac.pre-install
- main/transmission/transmission-daemon.pre-install
- main/ympd/ympd.pre-install
- main/znc/znc.pre-install
- testing/at/at.pre-install
- testing/buildbot-slave/buildbot-slave.pre-install
- testing/buildbot/buildbot.pre-install
- testing/clapf/clapf.pre-install
- testing/cluster-glue/cluster-glue.pre-install
- testing/dbmail/dbmail.pre-install
- testing/dspam/dspam.pre-install
- testing/ejabberd/ejabberd.pre-install
- testing/emby/emby.pre-install
- testing/mongodb/mongodb.pre-install
- testing/opensips/opensips.pre-install
- testing/pdns/pdns.pre-install
- testing/prosody/prosody.pre-install
- testing/qpage/qpage.pre-install
- testing/rrdbot/rrdbot.pre-install
- testing/wt/wt.pre-install
- unmaintained/ejabberd-git/ejabberd-git.pre-install