EFI systems typically don't support booting off ISO 9660 filesystems,
even if written to USB sticks. This patch adds support for generating a
GPT that covers the stick as well, with an additional partition entry
pointing purely at the secondary El Torito image. When burned to CD the
secondary El Torito will be used as an EFI boot image, and when written
to a USB stick the GPT partition will be found and may be booted from.

However, some earlier EFI Macs don't support booting from El Torito
images via EFI. To cater for them this also supports generating an Apple
partition table, allowing a third El Torito image in HFS+ format to be
made available to the firmware. This requires padding the MBR images
slightly in order to leave space for the Apple header, but should have
no functional impact.

Sadly, this breaks the workaround for Acer BIOSes (magic xor
instruction) when Mac support is enabled via -m... not much that can
be done about that.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

Move the MCONFIG files into a mk/ directory and give them more
descriptive names.

This is purely a cosmetic change to make the 'include' directives a
bit more coherent by making it obvious exactly which MCONFIG file
we're including. For example, in com32/lua/src/Makefile we exchange
the line,

	include ../../MCONFIG

for the much more comprehensible,

	include $(MAKEDIR)/com32.mk

Signed-off-by: Matt Fleming <matt.fleming@linux.intel.com>

Also numerous uses of *w opcodes and spacing fixes

This mbr code entity shows DL, DS, SI, 16 bytes of [DS:SI], ES, DI,
4 bytes of [ES:DI], and scans F0000h-FFFFFh on 16 byte alignment for $PnP.

This is useful for testing when MBR or VBR/PBR handoff goes awry.

Apparently some BIOSes (including some Acer Travelmate machines)
require an MBR to start with 0x33; apparently Micro$oft MBRs start
with 33 C0, an alternate coding of the "xorw %ax,%ax" instruction.  As
such, follow suit to work on these braindead BIOSes.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>