* include/grub/i386/pc/kernel.h: Define GRUB_KERNEL_MACHINE_DATA_END to
indicate end of data section in kernel image.
* include/grub/i386/efi/kernel.h: Define GRUB_KERNEL_MACHINE_PREFIX and
GRUB_KERNEL_MACHINE_DATA_END.
* kern/i386/pc/startup.S: Do not initialize grub_prefix, only reserve
space for it.
* kern/i386/efi/startup.S: Likewise.
* util/i386/pc/grub-mkimage.c: Initialize grub_prefix to /boot/grub
during image generation. Implement --prefix option to override this
patch.
* util/i386/efi/grub-mkimage.c: Likewise.
* util/update-grub_lib.in (convert_system_path_to_grub_path): Split
code to make path relative to its root into a separate function.
* util/i386/pc/grub-install.in: Use newly provided
make_system_path_relative_to_its_root() to convert ${grubdir}, then
pass the result to grub-install --prefix.