Add getlabelusesmbr(), as proposed in
http://mail-index.netbsd.org/tech-userlevel/2011/08/25/msg005404.html
This is used by disk tools such as disklabel(8) to dynamically decide is
the undelyling platform uses a disklabel-in-mbr-partition or not
(instead of using a compile-time list of ports).
getlabelusesmbr() reads the sysctl kern.labelusesmbr, takes its value from the
machdep #define LABELUSESMBR.
For evbmips, make LABELUSESMBR 1 if the platform uses pmon
as bootloader, and 0 (the previous value) otherwise.

If cpu_disklabel includes struct dkbad, define __HAVE_DISKLABEL_DKBAD.
This allows use of subr_disk_mbr on all archs. Default to it for
the rump disk component. No functional change for regular kernels.
(The other option would've been to include dkbad in disklabels
everywhere, but arguably this approach has less possible side-effects,
especially given that wedges and related magic will take over the
world any second now).

branches: 1.9.78;
merge ktrace-lwp.

Make disklabel(8) and fdisk(8) into "host tools " last step: build
and install ${TOOLDIR}/bin/${MACHINE_GNU_PLATFORM}-disklabel,
${TOOLDIR}/bin/${MACHINE_GNU_PLATFORM}-fdisk by "reaching over" to
the sources in ${NETBSDSRCDIR}/sbin/{disklabel fdisk}/.

To avoid clashes with a build-host's header files, especially on
*BSD, the host-tools versions of fdisk and disklabel search for
#includes such as disklabel.h, disklabel_acorn.h, disklabel_gpt.h,
and bootinfo.h in a new #includes namespace, nbinclude/. That is,
they #include <nbinclude/sys/disklabel.h>, <nbinclude/machine/disklabel.h>,
<nbinclude/sparc64/disklabel.h>, instead of <sys/disklabel.h> and
such. I have also updated the system headers to #include from
nbinclude/-space when HAVE_NBTOOL_CONFIG_H is #defined.

branches: 1.7.10;
remove boot_block stuff from include/disklabel.h, and migrate to
alpha_boot_block stuff in dev/dec/dec_boot.h

branches: 1.6.6; 1.6.8;
Fix doubled 'the's in comments.

branches: 1.5.2; 1.5.8;
clean up slightly, do a little #define trick to make checksumming
the boot block a little easier/more 'clean', and provide a macro to
checksum the boot block.

define 'struct boot_block' which is the alpha (SRM) boot block

clean up NetBSD RCS ID strings

add bad sector information to cpu disklabel

branches: 1.1.4;
preliminary Alpha support. note that NOT ALL OF THE MODIFICATIONS TO
THE REST OF THE KERNEL ARE IN THE TREE YET. Also, some of this is
_incredibly_ hack-ish, etc., but it works.