I18n: Update translation cs (100%).

74 translated messages.

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

74 translated messages.

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

74 translated messages.

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