I18n: Update translation pl (100%).

111 translated messages.

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

111 translated messages.

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

111 translated messages.

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