re-synchronize zfs man pages with illumos

[Andriy Gapon]

Originally ZFS manual pages were written using a different formatting language
from what we use in FreeBSD.  I am not very knowledgeable in this area, but the
experts should recognize the language by things like \fB, \fR, etc.

Martin Matuska (mm) converted the manuals to the FreeBSD mdoc in r228019
https://svnweb.freebsd.org/base?view=revision&revision=228019

Recently illumos switched to using mdoc format as well.
That happened gradually and the changes were usually mixed with other changes.
For example, the zpool manual was converted in this change:
https://svnweb.freebsd.org/base?view=revision&revision=318936
https://github.com/illumos/illumos-gate/commit/c8323d4323a565676ba44883bfeb289d9ed8813e

It is not surprising, of course, that the illumos mdoc pages are quite different
from their FreeBSD counterparts given the independent conversions.

So, at the moment we have several classes of differences that are not easy to
identify via textual differences of the source files alone.

1. Differences in the content due to underlying differences between illumos and
FreeBSD, e.g. zones vs jails or different sample disk names, etc.

2. Whitespace differences where exactly the same words are split differently
between the lines, etc.

3. Style differences.  For example, explicit parentheses vs Pq/Po/Pc; use of  Tn
in FreeBSD; much more frequent use of Ns macro in illumos; quotes vs a different
font (e.g. Qq vs Sy); etc.

4. Mistakes in either FreeBSD or illumos version.  For example, the FreeBSD
versions often continue a line after a period.

5. Independent / diverging language corrections.

My impression is that the illumos pages are cleaner than the FreeBSD ones at the
moment. My inclination is to suggest that we "restart" our pages from the
current illumos pages and "rebase" FreeBSD-specific changes on top of those.

I realize that that would be a lot of work.  But the benefits are quite obvious
as it would be much easier to merge changes both ways.

Comments, suggestions, offers of help are all very welcome!
Thanks.
-- 
Andriy Gapon