This just code loads one language at a time in an idle,
to avoid blocking the UI for a long time. The function returns
the id of the sources, so you can just call g_source_remove()
if you don't need the languages anymore (e.g if the user goes
to another panel before the list is fully populated).
https://bugzilla.gnome.org/show_bug.cgi?id=643096
If software with "Chhattisgarhi" translations was loaded (such
as k3b), we would fail to load the language name for it, as we
were not parsing the ISO-639-3 database.
https://bugzilla.gnome.org/show_bug.cgi?id=641373
Make more of the code common one, so we can re-use it for
the region panel. Show the user's current locale first, as well
as the list of languages used by other users, followed by a separator.
