NASM 0.98.39, the last 0.98.x supported version, is known to
miscompile Syslinux; the fix is
b0e1d423dd3e174a92a1d7256aec4e9b701ece3c and was added in
NASM 0.99.06.  Since NASM 0.99.x were alpha test releases, require
NASM 2.00 which was the first "real" release after the fix.

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

Conflicts:
	core/bcopy32.inc
	core/cleanup.inc
	core/conio.inc

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

If we enable interrupts for the serial console, add a proper interrupt
handler.  Since we don't know what vector we'll end up using, or if we
are shared with other devices, simply hook *all* the interrupts and
poll the serial port then.

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

Add a pm_call convenience macro, instead of using stub routines
everywhere.  Stubs would still make sense if we have a routine which
gets invoked from a lot of places, though, since the pm_call expands
to 9 bytes as opposed to 3 bytes per call site plus a 10-byte stub.

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

Simplify the pm_call usage:

- pm_call now saves and restores all registers
  callees that want to return values in registers can mess with
  the frame on the stack
- the PM function now enters with EAX = EBP = RM stack
  (EAX for the use of C code, EBP for assembly)
- the RM stack frame matches com32sys_t
- pmcall.inc defined macros for the stack frame based on EBP

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

Move source files out of the root directory; the root is a mess and
has become virtually unmaintainable.  The Syslinux core now lives in
core/; the Linux and generic utilities has moved into utils/, and
copybs.com has moved into dos/; it had to go somewhere, and it seemed
as good a place as any.