options are in main makefile now

Experimentation reveals that gcc ignores -mrtd for the implicit
arithmetic functions (e.g. __udivdi3), but not for the implicit
memcpy() and memset() functions.  Mark the implicit arithmetic
functions with __attribute__((cdecl)) to compensate for this.

(Note: we cannot mark with with __cdecl, because we define __cdecl to
incorporate regparm(0) as well.)

allow the UNDI NIC interrupt to happen.

This reverts commit 9e7b165017.

already handled the INT13 call.

Add some of the missing parts to libkir.h.

us to round down the size for the relocation copy to the nearest 64kB
(+0x10 bytes); this just happened to work on most machines because the
last 64kB of the image is all-zeroes anyway (it's the .bss).

emulation support) for an unknown purpose, and breaks grub.

int13.h.

compressor fixup section.

bytes of useless zeroes in the final image.

link-time check for section overlaps.  (In order to avoid wasting
space in the executable image, .bss16 will overlap with the following
section, which is .text).

start of the non-prefix blocks in the loaded image, and rely on the
image ordering.  This should make introducing compression much easier.

"rep movsb".

in a long loop before giving up on them.  Record method which worked
and default to that method on next attempt.

Kill off use of etherboot.h outside drivers/net.

optimisation of only trying to do so when necessary.

number of (potentially very slow) gateA20_set operations.

Die with a fatal error if we are unable to set gate A20; if this fails
then we are bound to experience memory corruption at a later stage,
and I'd prefer to pick it up early.

the UNDI stack.

Ignore obviously invalid length combinations (as returned by
e.g. VMWare's PXE stack).

Limit to one packet per poll to avoid memory exhaustion.

Always send EOI; do not chain to BIOS's default interrupt handler.
They are just too unpredictable; at least VMware's seems to kill the
machine if you go anywhere near it.

Disable interrupts after return from PXENV_UNDI_ISR, just in case some
dumb PXE stack enables them.