Add SCSI REPORT TIMESTAMP and SET TIMESTAMP support.

This adds support to camcontrol(8) and libcam(3) for getting and setting
the time on SCSI protocol drives. This is more commonly found on tape
drives, but is a SPC (SCSI Primary Commands) command, and may be found
on any device that speaks SCSI.

The new camcontrol timestamp subcommand allows getting the current device
time or setting the time to the current system time or any arbitrary time.

sbin/camcontrol/Makefile:
Add timestamp.c.

sbin/camcontrol/camcontrol.8:
Document the new timestamp subcommand.

sbin/camcontrol/camcontrol.c:
Add the timestamp subcommand to camcontrol.

sbin/camcontrol/camcontrol.h:
Add the timestamp() function prototype.

sbin/camcontrol/timestamp.c:
Timestamp setting and reporting functionality.

sys/cam/scsi/scsi_all.c:
Add two new CCB building functions, scsi_set_timestamp() and
scsi_report_timestamp(). Also, add a new helper function,
scsi_create_timestamp().

sys/cam/scsi/scsi_all.h:
Add CDB and parameter data for the the set and report timestamp
commands.

Add function declarations for the new CCB building and helper
functions.

Submitted by: Sam Klopsch
Sponsored by: Spectra Logic
MFC After: 2 weeks