Since it was requested and is possible with up-to-date binutils, inclusion
of debug info in xen.efi is the remaining part here. The other changes here
are cleanup related to both the work here as well as the one to make
binutils fit for our purposes.
1: EFI: sections may not live at VA 0 in PE binaries
2: EFI: keep debug info in xen.efi
3: EFI: don't have an overly large image size