Add support for SCSI UNMAP commands to CTL.

This patch adds support for three new SCSI commands: UNMAP, WRITE SAME(10)
and WRITE SAME(16).  WRITE SAME commands support both normal write mode
and UNMAP flag.  To properly report UNMAP capabilities this patch also adds
support for reporting two new VPD pages: Block limits and Logical Block
Provisioning.

UNMAP support can be enabled per-LUN by adding "-o unmap=on" to `ctladm
create` command line or "option unmap on" to lun sections of /etc/ctl.conf.

At this moment UNMAP supported for ramdisks and device-backed block LUNs.
It was tested to work great with ZFS ZVOLs.  For file-backed LUNs UNMAP
support is unfortunately missing due to absence of respective VFS KPI.

Reviewed by:	ken
MFC after:	1 month
Sponsored by:	iXsystems, Inc
Explicitly initialize 'vmname' to NULL.

Reviewed by:	grehan
Quick mdoc/whitespace/spelling pass, this needs some more work.
Handle single-byte reads from the bvmcons port (0x220) by returning
0xff.  Some guests may attempt to read from this port to identify
psuedo-PNP ISA devices.  (The ie(4) driver in FreeBSD/i386 is one
example.)

Reviewed by:	grehan
Merge OpenSSL 1.0.1g.

Approved by:	benl (maintainer)