We have historically run the comboot API with interrupts off due to
concerns about stack overflow.  However, this is a really bad idea: we
can easily spend a fair bit of time servicing one of these routines,
especially when doing things like waiting for I/O.

In particular, do_idle should *never* be run with interrupts disabled.

Switch to running with interrupts enabled everywhere unless we have
specific reasons not to do so.

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

Try to HLT the processor during idle.  All the events we care about
should have interrupts associated with them, except possibly the
serial console.  Try to deal with the serial console by waiting some
time before going into HLT, and giving the user the option of enabling
the serial console interrupt, on the assumption that the BIOS will
simply IRET.

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

MDSLINUX (Multiple Disk Syslinux) will never happen, kill references
to it.

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

We cannot realistically realign comboot_seg without breaking com16
modules (which have the DOS-derived assumption that they own the rest
of low memory.)  However, we can use xfer_buf_seg as the com32 bounce
buffer, which allows us to retain the benefit of a 64K-aligned buffer.

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

vgafontbuf is one of the largest (bss) structures in the zero segment,
together with the trackbuf (which we realistically can't move.)
Create a new "auxilliary segment" for fixed-sized data which needs to
be in the low megabyte, but not necessarily in the zero segment.

This pushes up the low memory usage, but only by 8K.

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

Add a new macro "alignz" to align with zero bytes; use to align inside
a data section (i.e. a progbits section which doesn't contain code.)

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

ipappend information is needed for the plain cmdline too, since it may
be used by linux.c32.  While we're at it, clean up the handling of
ipappend lines -- we can rather obviously use a loop for them.

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

Conflicts:
	com32/lib/syslinux/memmap.c

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

Update copyright notices.  Per agreement with my new employer, Intel
Corporation, add Intel copyright notices where appropriate.

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