docs/162775: zpool(1): Document some undocumented zpool import options

[bcr at FreeBSD.org]

Synopsis: zpool(1): Document some undocumented zpool import options

Responsible-Changed-From-To: freebsd-doc->mm
Responsible-Changed-By: bcr
Responsible-Changed-When: Mon Jun 4 19:46:25 UTC 2012
Responsible-Changed-Why: 
This should be checked by someone more familiar with ZFS code.

I've compared the zpool(8) synopsis with the case labels from the PR
description and I've found that the last three options (T, V, X) are
not there.

@mm: Can you take a look at this? Thanks! 

http://www.freebsd.org/cgi/query-pr.cgi?pr=162775