Fix image saving for streams with characters not supported in path names.

This commit fixes #4011.
Update translations from Transifex:

 - Galician
 - Japanese
 - Romanian
 - Vietnamese
Language menu: Ensure "Language" always appears in English in menu entry.

If "Language" doesn't appear in the translated string, "(Language)" will be appended automatically.
Language menu: Use submenus to group language names starting with the same character.
Update translations from Transifex:

 - Greek.