Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r235317:

General mdoc(7) and typo fixes.

PR: 167776

Merge r228039 from head to stable/9:

Add an introductory Capsicum man page providing a high-level description of
its mechanisms, pointing at other pertinent man pages, and cautioning about
the experimental status of Capsicum in FreeBSD.

Sponsored by: Google, Inc.

Approved by: re (kib)

Add an introductory Capsicum man page providing a high-level description of
its mechanisms, pointing at other pertinent man pages, and cautioning about
the experimental status of Capsicum in FreeBSD.

MFC after: 3 days
Sponsored by: Google, Inc.