Move the relocated boot1 and arg transfer space from 0x600/0x800 to
0x700/0x900. In theory this should make no difference, apart from the fact
that Buslogic controllers happen to use a few bytes at 0x600 for some sort
of scratch space for it's int 0x13 hook (!!!), causing the machine to crash
badly when the boot2 code makes it's callbacks into boot1 for disk IO.
Submitted by: Robert Nordier <rnordier@freebsd.org>
interface. Do some general consistency fixes and space optimizations.
Use of some freed-up space to defend against possible BIOS misfeatures.
boot2: Revise disk read interface to provide for boot1 changes. Free
up space for this.
