Bugfixes in multiboot for bugs uncovered by solaris kernel.
* loader/i386/multiboot_elfxx.c (grub_multiboot_load_elf): Corrected
limit detection.
Use vaddr of correct segment for entry_point.
* loader/i386/multiboot.c (code_size): New variable.
(grub_multiboot): Define offsets by adding to `code_size' rather
than substracting from `grub_multiboot_payload_size'. Provide
4-byte alignment to MBI and others by increasing
`boot_loader_name_length' appropiately.
* loader/i386/multiboot_elfxx.c
(CONCAT(grub_multiboot_load_elf, XX)): Initialize `code_size'.
Factorize elf32 / elf64 code in Multiboot loader. This will
prevent it from getting out of sync again.
* loader/i386/multiboot.c (grub_multiboot_is_elf32,
grub_multiboot_load_elf32, grub_multiboot_is_elf64,
grub_multiboot_load_elf64): Move from here ...
* loader/i386/multiboot_elfxx.c (grub_multiboot_is_elf,
grub_multiboot_load_elf): ... to here (new file).
