Change from lkm to kld
Add field plexsdno to sd struct
Add flag VF_NEWBORN to drive, sd, plex and volume structs, indicating
that the object has just been created.
Add object types for raw (unattached) plexes and subdisks
Remove definitions of VOLNO, PLEXNO and SDNO (now functions Volno,
Plexno and Sdno)
Move revive parameters from struct plex to struct sd.
struct plex:
maintain a count of the number of inaccessible subdisks.
remove defective and unmapped regions.
Debug flags: make an enum (previously #define)
Set default revive block size to 64kB (was 32 kB)