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

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

Synchronize stable/9 Forth code with head via MFC of 22 revisions:
227727, 233941, 235560, 238431, 241310, 241361, 241363, 241365, 241367,
241523, 242667-242669, 242923, 243114, 243660, 244048, 244089, 244158,
253715, 254105, and 254108.

This includes critical fixes that sadly should have been merged prior.
Namely, SVN r244158 fixes a possible regression.

MFC r235873, r235967:

Fixes to man8 groff mandoc style, usage mistakes, or typos.

PR: 168016
Submitted by: Nobuyuki Koganemaru
Approved by: gjb (mentor)

MFC r232157, r232158:

r232157:
Fix various typos in manual pages.

Submitted by: amdmi3
PR: 165431

r232158:
Whitespace cleanup:
o Wrap sentences on to new lines
o Cleanup trailing whitespace

MFC r228985,229881:

Unset the environment variables associated with individual menu items
before invoking the kernel.

Get rid of a spurious warning on the console when booting the kernel
from the interactive loader(8) prompt and beastie_disable="YES" is set
in loader.conf(5).

Submitted by: Devin Teske <devin dott teske fisglobal.com>

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Restore behavior of the autoboot_delay="-1" boot menu setting to the
pre-r222417 state. The behavior was essentially reversed in r222417
which can cause confusion.

PR: 159775
Submitted by: Devin Teske
Approved by: re (kib)

New boot loader menus from Devin Teske.
Discussed on hackers and recommended for inclusion into 9.0 at the devsummit.
All support email to devin dteske at vicor dot ignoreme dot com .

Submitted by: dteske at vicor dot ignoreme dot com
Reviewed by: me and many others