Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r251743:
Improve firmware download status check. Previous check was insufficient for
ATA since it ignored transport errors like command timeouts, while for SCSI
it was just wrong.

MFC (part of) r241737 (ed):

More -Wmissing-variable-declarations fixes.

In addition to adding `static' where possible:

...
- sbin/camcontrol: Move `verbose' into camcontrol.h and fix shadow warnings.
...

Merge the firmware download functionality into camcontrol, as well as
several other minor code changes.

Obtained from: Netflix, Inc.

Add firmware update support for SCSI devices.

Firmware can be reprogrammed on devices from Hitachi, HP, IBM, Plextor,
Quantum, and Seagate. At least one device from each manufacturer has
been tested with some version of this code, and it has been used to
update thousands of drives so far.

The man page suggests having a backup of the drive's data, and the
operation must be confirmed, either interactively or on the command
line. (This is the same as the confirmation on the format command.)

This work is largely derived from fwprog.c by Andre Albsmeier.

Submitted by: Nima Misaghian
Sponsored by: Sandvine Incorporated
MFC after: 3 months