* kern/ieee1275/init.c (grub_machine_set_prefix): If `grub_prefix'
is non-empty, use it to set the `prefix' environment variable instead
of the usual approach.
* kern/i386/linuxbios/init.c (make_install_device): Remove function.
(grub_machine_set_prefix): Use `grub_prefix' to set the `prefix'
environment variable instead of dummy make_install_device().
* kern/i386/ieee1275/startup.S: Include `<grub/machine/kernel.h>'.
(start): Insert a data section, with `grub_prefix' variable.
* kern/i386/linuxbios/startup.S: Likewise.
* include/grub/powerpc/ieee1275/kernel.h [!ASM_FILE] (grub_prefix):
New variable reference.
* include/grub/i386/ieee1275/kernel.h (GRUB_KERNEL_MACHINE_PREFIX):
New macro. Defines offset of `grub_prefix' within startup.S (relative
to `start').
(GRUB_KERNEL_MACHINE_DATA_END): New macro. Defines the end of data
section within startup.S (relative to `start').
* include/grub/i386/coreboot/kernel.h: Likewise.
* util/elf/grub-mkimage.c (add_segments): Receive `prefix' parameter.
Overwrite grub_prefix with its contents, at the beginning of the
first segment.
(main): Understand -p|--prefix.
