Changes to boot code to relocate the MBI.

Changes to boot code to relocate the MBI.

This fix relocates the MBI and associated data to safe
memory locations before paging is enabled. This fixes the
issue with GRUB2 loading chunks of the MBI at very high
phys. addresses. These fixes are from xen-unstable change-
sets 19146 and 19158.

 Changes to be committed:
   (use "git reset HEAD <file>..." to unstage)

	modified:   xen/arch/x86/Makefile
	modified:   xen/arch/x86/boot/Makefile
	new file:   xen/arch/x86/boot/build32.mk
	modified:   xen/arch/x86/boot/head.S
	new file:   xen/arch/x86/boot/reloc.c