I18n: Update translation ast (93%).

265 translated messages, 18 untranslated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
I18n: Update translation sl (84%).

238 translated messages, 45 untranslated messages.

Transifex (https://www.transifex.com/projects/p/xfce/).
I18n: Update translation sl (92%).

263 translated messages, 20 untranslated messages.

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