(svn r7388) -Fix (r7384 / r7368 / r3757): When adding a new news item for the first time (_latest_news
is INVALID_NEWS), make it the value of _oldest_news, not zero as DeleteVehicleNews can
change _oldest_news. Also remove the (i == INVALID_NEWS) return 0; guard from increaseIndex
as it's only used in 2 places, nowhere else.