Fail gracefuly when attempting to load 64-bit kFreeBSD on IA32 CPU.
* include/grub/i386/cpuid.h: New file.
* commands/i386/cpuid.c: Include `<grub/i386/cpuid.h>'.
(has_longmode): Rename to ...
(grub_cpuid_has_longmode): ... this. Update all users. Remove
`static' attribute.
* loader/i386/bsd.c: Include `<grub/i386/cpuid.h>'.
(grub_bsd_load_elf): Fail if load of 64-bit kernel was requested
on a CPU that doesn't implement AMD64 instruction set.