It was previously an important part of DVDInterface,
but since its usage there was replaced with DVDThread,
the only remaining uses of it are in Boot and Boot_BS2Emu.
Replaces them with forward declarations of used types, or removes them entirely if they aren't used at all. This also replaces certain Common headers with less inclusive ones (in terms of definitions they pull in).
* The file already exsists, otherwise we wouldn't have gotten
this far in the boot.
* We have already checked if it's a Wii or GameCube elf,
besides, it's too late to change our minds now anyway.
* On Wii - Don't call EmulatedBS2, it can never succeed as
it knows nothing about booting elfs. Just call the
SetupWiiMemory directly if needed.
* On GameCube - We still call EmulatedBS2_GC, but we stop
it from running Apploader, which might boot something
unexpected from the default iso or DVD root folder.
