Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

Fix panic in ng_patch(4) caused by checksum flags being added to mbuf flags.

Tested by: Maxim Ignatenko <gelraen.ua@gmail.com>
Approved by: kib(mentor)

MFC after: 3 days

Use M_WAITOK flag instead M_WAIT for malloc.

Suggested by: glebius
MFC after: 1 week

* Include sys/systm.h for KASSERT()
* Remove unneeded includes and comment
* Replace home made OFFSETOF() macro with standard offsetof()

Pointed out by: bde
Approved by: kib (mentor)

Style(9) fixes:
* Sort includes
* Replace #define<SPACE> to #define<TAB>
* Split declarations and initializations
* Split long lines

Requested by: kib
Approved by: kib (mentor)
MFC after: 1 month

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