I'm an idiot.   All the body of rzdump() is inside an #ifdef notdef,
and it contains code that looks suspciously like the hp300 scsi
dump routine.  No wonder it never produced a crashdump.

I've taken the #ifdef notdef out, and hacked it so that everything
except the actual write-a-block code  compiles.

Is it reasonable to assume that blocks in aa swap partition can always
be read (or written) with a 6-byte SCSI command, instead of a 10-byte
group1 extended command?   I hope so...

Also, what's a good way to force a crashdump?   Is adding a -d option
(meaning do RB_DUMP) to /sbin/reboot  a reasonable option?

--Jonathan