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

Note: haproxy now requires openssl as it supports SNI

- move default config location to /etc/haproxy/
- provide install/upgrade script that moves existing config to new
  location
- provide dummy config
- create haproxy user and group