hinge on the "verb" parameter which the class gets to interpret as
it sees fit.
Move the entire request into the kernel and move changed parameters
back when done.
kern.geom.conftxt, which md disks don't show up in. If the magic and
the checksum are right assume its a valid sunlabel, otherwise use the
DIOC ioctls to get the disk parameters and whip up a label out of thin
air.
- Don't just silently create or correct invalid c partitions, warn about
invalid ones in label proto files.
- Split checksumming into a function since we do it a couple times. Also
don't include the sl_cksum field in the checksum, which avoids needing
to clear it first.
This is makes sunlabel a suitable replacement for disklabel in make release.
