Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Switch the default WARNS level for sbin/ to 6.

Submitted by: Ulrich Spörlein

Make recoverdisk compile on amd64 and possibly other 64bit archs.
Bump WARNS to 6.

PR: amd64/97566
Reviewed by: phk@
MFC after: 3 days

o Take an account a media sectorsize for medium and bigsize calculation.
o Introduce -r and -w keys which allow to load and save a worklist.
o Replace README by man page.

PR: bin/96677
Submitted by: Ulrich Spoerlein
Approved by: phk
MFC after: 1 month

Start the dreaded NOFOO -> NO_FOO conversion.

OK'ed by: core

For variables that are only checked with defined(), don't provide
any fake value.

This is a small tool which will read an entire disk(partition) using
1M blocks and optionally write the read data to a file or disk.

If a read error happens, the 1M block gets put on the end of the worklist
and will be retried with 64k blocksize.

If a read error happens again, the 64k block gets put at the end of the
worklist and will be retried with single sector reads.

The program keeps trying until you stop it.

You can refresh a disk:

recoverdisk /dev/ad1 /dev/ad1

or salvage a floppy:

recoverdisk /dev/fd0 myfloppy.flp