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

module/nvpair/nvpair.c

@@ -2395,7 +2395,7 @@ nvlist_xpack(nvlist_t *nvl, char **bufp, size_t *buflen, int encoding,
 	 * 1. The nvlist has fixed allocator properties.
 	 *    All other nvlist routines (like nvlist_add_*, ...) use
 	 *    these properties.
-	 * 2. When using nvlist_pack() the user can specify his own
+	 * 2. When using nvlist_pack() the user can specify their own
 	 *    allocator properties (e.g. by using KM_NOSLEEP).
 	 *
 	 * We use the user specified properties (2). A clearer solution