Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Fix a bunch of typos and spelling mistakes.

More mdoc nitpicking to improve compatibility to mdocml

- .Nd in section NAME is not optional
- .Ed was missing
- "indent" is not a flag, but a literal argument for -offset
- stop switching font sizes for acronyms
- use .Brq instead of rolling our own

mdoc: move CAVEATS, BUGS and SECURITY CONSIDERATIONS sections to the
bottom of the manpages and order them consistently.

GNU groff doesn't care about the ordering, and doesn't even mention
CAVEATS and SECURITY CONSIDERATIONS as common sections and where to put
them.

Found by: mdocml lint run
Reviewed by: ru

- Improve wording.
- ae(4) first appeared in 7.1. Reflect this.

Approved by: kib (mentor)
MFC after: 1 week

- Minor mdoc cleanup.
- Make HARDWARE section a bit more friendly for the Hardware Notes.

- Add manual page for ae(4) driver.

Approved by: kib (mentor)
MFC after: 1 week