I18n: Update translation ar (100%).

170 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
I18n: Update translation tr (100%).

170 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
I18n: Update translation cs (100%).

170 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
I18n: Update translation pl (100%).

170 translated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).