Remove/separate any 2.11 disk layout stuff, e.g labels.

So tinyboot and copy themselves can only access tape records and whole
disks.

Build 2.11 versions of mkfs, restor, icheck and disklabel.

Ditto for 6th and 7th Edition.

A user-mode (real program) version of a tape client, something like

	vtclient -r /dev/ttya 0

to read record 0 from /dev/ttya, pipe to stdout.

Port uncompress to 6th and 7th Editions, so:

	vtclient -r /dev/ttya 4 | uncompress -c | tar vxf -
