Turn it_IT.po and it.po into just it.po

Submitted by sco..@..il.com

Assigned to Jannis Pohlmann

Link to original bug (#15548)

Description

There are both: po/it.po po/it_IT.po

The strings are different.

Only thunar-archive-plugin and xfdashboard have it_IT.po the rest uses it.po so i suggest using it.po. But i dont know if the strings from it.po or it_IT.po should be in the new it.po.