need subr_disklabel.c

branches: 1.9.18;
Add a COMMENT describing what each component roughly does.

"make describe" prints the comment.

Requested/inspired by Vincent Schwarzer on rumpkernel-users

Satisfy yet another non-modular driver still requiring a manual init call.

branches: 1.7.20; 1.7.38;
Globally define -Wno-pointer-sign, as it has become a pointless
exercise of "add it to every Makefile individually".

XXX: should autosynchronize with the rest of the kernel buildflags
in sys/conf/Makefile.kern.inc.

branches: 1.6.2;
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).

kern_physio is already provided by rumpvfs

Build proper version for i386 (since it works) and dummy versions
for the rest until the disklabel MD problems get sorted out.

librumpdev_disk doesn't compile on a lot of platforms, so replace
it with a dummy for now until I can work out the problems (nothing
in-tree links against it yet).

remember to build opendisk

branches: 1.1.2;
Checkpoint a bunch of work-in-progress: support for disk devices
and raidframe. Raidframe works well enough to configure a raid in
the rump kernel, but the usage is "interesting" (pending some other
changes/cleanup from other parts in my tree).

These are not built by default yet.