Improve FreeDOS direct loading support compatibility.

	Improve FreeDOS direct loading support compatibility.

	* include/grub/i386/relocator.h (grub_relocator16_state):
	New member ebp.
	* grub-core/lib/i386/relocator.c (grub_relocator16_ebp): New extern
	variable.
	(grub_relocator16_boot): Handle %ebp.
	* grub-core/lib/i386/relocator16.S: Likewise.
	* grub-core/loader/i386/pc/freedos.c:
	Load BPB to pass kernel which partition to load from.
	Check that kernel file is not too large.
	Set register dl to BIOS unit number as well.