Merged revisions 1832-1836 from stable (added dovecot support for debian squeeze and added a new distid and class for debian6 specific modifications.

Added Support for Sieve mail filtering language on dovecot servers.

Implemented: FS#973 - Gentoo support for installer. Fixed FS#974 - Directory mode for firewall configuration

Check if the mysql_connect function exists in the installer.

Added a missing language string in server config form.

Added: interface module web traffic statistics
Fixed: mail_traffic is now reported to master server instead of local
Fixed: GRANTs for slave server database user on master database

- checking for running instance in server.php

sh: /etc/init.d/apache2: No such file or directory

Fixed a bug that prevented the restarting of services when the install is finished.

- Update server.ini during install
- Changed default vmail directory form /home/vmail to /var/vmail

Fixed #250. Services are only restarted if a startscript is defined in the $config variable during installation or update.

Added a notice to the installer to choose 'y' for apache configuration if the server shall run the interface.

Fixed bugs in installer.
A backup file of the database is stored in /root during update.

Changed the installer code to use the global $conf array in all installer functions instead of the $conf member variable of the $inst object to fix bug #187.