We generally have no reason to call these functions on our own, so
there's not much reason to declare them, especially not in the cpp
file where they're defined. In case we ever do get a reason to do
it, we can add declarations for just the functions that need them.
Deduplicates code, and gets rid of some problems the old code had
(such as: bad performance when calling native functions, only one
disc showing up for multi-disc games, Wii banners being low-res,
unnecessarily much effort being needed for adding more metadata).
