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 r255459:
Remove documentation describing functionality which geom(4) does not,
in fact, provide.

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

Approved by: re (implicit)

mdoc: order prologue macros consistently by Dd/Dt/Os

Although groff_mdoc(7) gives another impression, this is the ordering
most widely used and also required by mdocml/mandoc.

Reviewed by: ru
Approved by: philip, ed (mentors)

Add links to libgeom(3) where appropriate.

Fix a typo and add manpage links to geom(4).

Approved by: rwatson (mentor)

Clarify that G_F_DISKIOCTL is unused, and remove G_T_DETAILS altogether,
since it isn't actually #defined.

Discussed with: phk

Clean up the grammar in here some.

-mdoc sweep.

Assorted markup fixes and minor wordsmithing.

Approved by: re

Document the GEOM debug flags.

Mechanically kill hard sentence breaks and double whitespaces.

Don't confuse "GEOM" with "geom".

Approved by: phk

Kill whitespace at EOL.

Approved by: re (blanket)

A few stylistic fixes.

Try to clarify how orphaning works.

english(4) police.

Uniformly refer to a file system as "file system".

Approved by: re

mdoc(7) police: Use the default .Os version.

Approved by: re

Stamp out Danglish: Spelling, grammer and other nitpicking.

Submitted by: "Steven G. Kargl" <kargl@troutmask.apl.washington.edu>

mdoc(7) police: remove whitespace at EOL.

First cut at a geom(4) manpage.

The mdoc markup and all spelling errors in this file are all legal game
for anyone with more doc-clue than me.