Merge branch 'stable-3.1' into 'stable-3.1'

install/dist/lib/debian60.lib.php

install/lib/install.lib.php

install/lib/installer_base.lib.php

install/sql/incremental/upd_dev_collection.sql

install/sql/ispconfig3.sql

install/tpl/debian6_dovecot.conf.master

install/tpl/debian6_dovecot2.conf.master

install/tpl/debian_dovecot.conf.master

install/tpl/debian_dovecot2.conf.master

install/tpl/debian_postfix.conf.master

install/tpl/fedora_dovecot.conf.master

install/tpl/fedora_dovecot2.conf.master

install/tpl/fedora_postfix.conf.master

install/tpl/gentoo_postfix.conf.master

install/tpl/master_cf_amavis10025.master

install/tpl/master_cf_amavis10027.master

install/tpl/opensuse_dovecot.conf.master

install/tpl/opensuse_dovecot2.conf.master

install/tpl/opensuse_postfix.conf.master

interface/web/mail/mail_user_edit.php