- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Added the IPLware 3.33 support.
- Added magic numbers to pretend the NEC original program version
2.70.
- Added string display routine with Shift-JIS code support.
- Added three nop instructions at start1 in start.s since the
installaer of the IPLware put 'call $0x09ab' instruction.
- Put the near return instruction at 0x9ab in selector.s.

Since the Shit-JIS display routine must be located at 0x1243, the
linker script file (ldscript) is applied.

IPLware support. The `IPLware' program assumes boot menu program
begins with the `jmp 0x2d4' near jump.

Added PC-98 HDD boot manager. The boot0 is the `IPL' which occupies
sector 0 of a disk and boot0.5 is the `boot selector' which starts
from address 0x400. The IPL loads boot0.5 and boot0.5 loads bootblock
of a slice.

The boot manager stuff was developed by me (kato) with Borland C++,
and then, translated into bcc in the ports collection by Nokubi-san.
After that, boot0 has been translated into gas with the .code16
directive by Takahashi-san (nyan) and boot0.5 has been rewritten in
gas by me.