Stop building a.out kernels so that mkldscript.sh is no longer necessary.

Tested "build.sh release", and the default ELF GENERIC kernel loaded by
the native bootloader just works on LUNA-II.

Revive NetBSD/luna68k.

Even after almost a lost decade since NetBSD/luna68k was
switched to using ELF format by default back in 2001,
actually only one fix (bus.h) is required for a GENERIC kernel itself
to get multiuser login: prompt on a real hardware. Hurrahhh!!!

Demonstrated with a working Xorg mono server on the NetBSD booth
at Open Source Conference 2011 Kansai @ Kyoto:
http://www.ospn.jp/osc2011-kyoto/

"Very impressed," commented by Tomoko YOSHIDA,
Program Committee Chair of the Conference,
and some other OMRON guys.

Special Thanks to Tadashi Okamura, for providing
a working SX-9100/DT "LUNA" for this mission.


Changes details:

sys/arch/luna68k/include/bus.h
- handle stride properly even on multi and region ops for MI spc(4)
- also fix stride handling of (currently unused) 2 and 4 byte ops

sys/arch/luna68k/conf/Makefile.luna68k
sys/arch/luna68k/conf/kern.ldscript.head
sys/arch/luna68k/conf/kern.ldscript.tail
- build a faked a.out kernel using elf2aout(8) tool
and a linker script derived from cats and shark
for the LUNA firmware that loads a.out binary directly
via network or from a UNIOS partition on a local disk

sys/arch/luna68k/dev/omrasops.c
sys/arch/luna68k/dev/omron_rfont.h
- use the original OMRON font derived from 4.4BSD-Lite/luna68k
rather than gallant19 which is used on Sun workstations
(XXX omrasops.c should be rewritten to use generic wsfont(4))

distrib/luna68k/*
distrib/utils/sysinst/arch/luna68k/*
etc/etc.luna68k/MAKEDEV.conf
etc/etc.luna68k/Makefile.inc
sys/arch/luna68k/conf/INSTALL
- build a ramdisk based INSTALL kernel with sysinst(8) for luna68k
- also build an installation iso image for luna68k

sys/arch/luna68k/conf/GENERIC
- enable SYSVSHM (and other SYSV*) options for Xorg server

More Xorg changes (which need some more cleanup) and
isiboot.c fixes will come soon.