install() now calls relocate(), moves the protected-mode code to the new
location, and calls hide_etherboot().

int13_boot() now does its own segment register save and restore, ready
for the removal of segment register restoration from the libkir
generic code.

Tidied up debug messages; the log now contains one line per INT 13
operation, looking like

 INT 13,08 (80): Get drive parameters
 INT 13,02 (80): Read: C/H/S 0/47/14 = LBA 0xb9e <-> 1084:0000 (count 106)

the kernel), which encapsulates the information needed to refer to an
external buffer.  Under normal operation, this can just be a void *
equivalent, but under -DKEEP_IT_REAL it would be a segoff_t equivalent.

Use this concept to avoid the need for bounce buffers in int13.c,
which reduces memory usage and opens up the possibility of using
multi-sector reads.

Extend the block-device API and the SCSI block device implementation
to support multi-sector reads.

Update iscsi.c to use user buffers.

Move the obsolete portions of realmode.h to old_realmode.h.

MS-DOS now boots an order of magnitude faster over iSCSI (~10 seconds
from power-up to C:> prompt in bochs).

linear calls to load the MS-DOS boot sector in my test setup.

don't conform to BBS (e.g. the one created by mkdosfs).

interrupts hooked.

devices).

Add method for hooking real-mode interrupt vectors.