OpenZFS 7812 - Remove gender specific language

Authored by: Daniel Hoffman <dj.hoffman@delphix.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Steve Gonczi <steve.gonczi@delphix.com>
Reviewed by: Chris Williamson <chris.williamson@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Igor Kozhukhov <igor@dilos.org>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed-by: Giuseppe Di Natale <dinatale2@llnl.gov>
Ported-by: George Melikov <mail@gmelikov.ru>

This change removes all gendered language that did not refer specifically
to an individual person or pet. The convention taken was to use
variations on "they" when referring to users and/or human beings, while
using "it" when referring to code, functions, and/or libraries.
Additionally, we took the liberty to fix up any whitespace issues that
were found in any files that were already being modified.

OpenZFS-issue: https://www.illumos.org/issues/7812
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/ad626db
Closes #5822