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 r233648:
Remove trailing whitespace per mdoc lint warning

Approved by: cperciva (implicit)

MFC r235319:

Remove duplicate words in mdoc(7) pages.

PR: 167810

Merge 232538:
Fix ng_ipfw(4) cookie number in example.

Pointed out by: "Jacco van Buuren" <jaccovanbuuren gmail.com>

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

Approved by: re (implicit)

New netgraph node ng_patch(4). It performs data modification of packets
passing through. Modifications are restricted to a subset of C language
operations on unsigned integers of 8, 16, 32 or 64 bit size.
These are: set to new value (=), addition (+=), subtraction (-=),
multiplication (*=), division (/=), negation (= -), bitwise AND (&=),
bitwise OR (|=), bitwise eXclusive OR (^=), shift left (<<=),
shift right (>>=). Several operations are all applied to a packet
sequentially in order they were specified by user.

Submitted by: Maxim Ignatenko <gelraen.ua at gmail.com>
Vadim Goncharov <vadimnuclight at tpu.ru>
Discussed with: net@
Approved by: mav (mentor)
MFC after: 1 month