Pull up following revision(s) (requested by manu in ticket #1038):
sys/dev/vnd.c: revision 1.252
sys/dev/vnd.c: revision 1.253
sys/dev/vnd.c: revision 1.254
sys/dev/vnd.c: revision 1.249
sys/sys/disk.h: revision 1.66
sys/dev/vnd.c: revision 1.250
sys/dev/vnd.c: revision 1.251
- Add DK_DEV_BSIZE_OK()
- Simplify ioctl handling a little.
- disable debugging
- Return ENXIO if the get ioctl exceeds the number of configured devices.
  XXX: pullup-7
- explain why the int cast works (suggested by kre)
- fix incorrect memset.
- Use the new DK_DEV_BSIZE_OK() macro.

(riz)