I18n - Can't create lang column as varchar(5)

I need to override the LANG column size on i18n tables, so I can use "pt_BR" language. I'd like the LANG column to be varchar(5) and not char(5) as it happens if I modify the field length to 5.

I've also tried to set the "fixed" option as false, but I noticed that the I18n generator overrides this option (I18n.php - line 98).

The only workaround I could find was setting the length option as null and the type as varchar(5), but at least for me, it doesn't seem to be the most correct way to define it.

I'd suggest modifying the I18n table definition generator to not override this option.

I've attached a patch with the proposed fix.