* include/grub/multiboot2.h: Provide compatibility defines for
multiboot2.h.
* include/multiboot2.h: Include stdint.h only if needed, using
angle brackets.
* loader/i386/pc/multiboot2.c: Include multiboot2.h after
grub/multiboot2.h.
* loader/ieee1275/multiboot2.c: Likewise.
* loader/multiboot2.c: Likewise.
* loader/multiboot_loader.c: Likewise.
* kern/powerpc/ieee1275/init.c: Move from here ...
* kern/ieee1275/init.c: ... to here. Update all users.
* kern/powerpc/ieee1275/cmain.c: Move from here ...
* kern/ieee1275/cmain.c: ... to here. Update all users.
* kern/powerpc/ieee1275/openfw.c: Move from here ...
* kern/ieee1275/openfw.c: ... to here. Update all users.
* loader/powerpc/ieee1275/multiboot2.c: Move from here ...
* loader/ieee1275/multiboot2.c: ... to here. Update all users.