turning off COMPAT_386BSD_MBRPART in disklabel

[David Holland <dholland-tech%netbsd.org@localhost>]

PR 44496 notes that COMPAT_386BSD_MBRPART is still enabled in
disklabel(8), even though it was turned off by default in the kernel
early in 4.99.x. The PR also notes that it's not harmless to leave it
on.

I'm inclined to turn it off in disklabel(8) right now. There's no
particular reason to have it there if the kernel doesn't support it,
and since fixing up a really old disk doesn't require disklabel(8),
only fdisk(8) there doesn't seem to be any upgrade/compatibility
argument to have it in -6.

(I think at least until -6 is branched it would be prudent to leave the
code there but disabled, though.)

Does anyone object to this? I almost committed the change unilaterally
but decided that was pushing things a little.

-- 
David A. Holland
dholland%netbsd.org@localhost