Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC: r239063, r239064, r239069, r240852, r240854

- boot2: bunch of variables are turned into uint8_t.
- boot2: Remove unnecessary initializations.
- loader: replace ugly inb/outb re-implementations with cpufunc.h.
- Reduce diffs against i386.

MFC r235264: MFi386: improve argument passing via btxldr

MFi386: improve argument passing via btxldr

use related definitions in i386 bootargs.h

Reviewed by: nyan, jhb
MFC after: 1 month

MFi386: revision 1.4.

$Id$ -> $FreeBSD$

PC98 version of new boot loader. Because boot2 has not yet ported,
files in boot2 directory are copies from legacy biosboot.

Submitted by: IMAI Takeshi <take-i@ceres.dti.ne.jp>