8138 Improve manpage spelling

illumos/illumos-gate@bccbd30bb6d0c20635d3f23e8d63f3f8170d3c46
https://github.com/illumos/illumos-gate/commit/bccbd30bb6d0c20635d3f23e8d63f3f8170d3c46

https://www.illumos.org/issues/8138

While reading man pages, I've noticed a number of spelling mistakes
and simple typos we should fix.

Reviewed by: Toomas Soome <tsoome@me.com>
Reviewed by: Cody Mello <melloc@joyent.com>
Reviewed by: Patrick Mooney <patrick.mooney@joyent.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Peter Tribble <peter.tribble@gmail.com>