In zabbix forum, I have followed that zabbix has Turkish locale support at front end.
I have read the release note of 2.0.0 rc3 (http://www.zabbix.com/rn2.0.0rc3.php) and I saw there is an improvement for Turkish language (described in ZBX-1357).
I have downloaded wmware version (2.0.3) but couldn't see the turkish language support at front end (user profile section) when I login to front end.
When I dig into source code of front end. In directory of <root of front end>/include/ the file locales.inc includes turkish language description (// 'tr_TR' => _('Turkish (tr_TR)'),
) as commented.

Why turkish language support is discarded from front end although it's described that turkish language support is provided in 2.0.0 rc3?