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

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

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

Approved by: re (implicit)

Make the cookie constant name canonical.

/* -> /*- for license, minor formatting changes

Use a single style of multiple inclusion protection for Netgraph headers.

Reviewed by: archie, harti, emax

General cleanup providing better style(9) conformance and generally
improved readability. The two real functional changes are that
netgraph now sees this as the "split" node type rather then the
"ng_split" node type and that meta data is passed through without
processing rather then being dropped.

Reviewed by: jhb, julian
MFC after: 7 weeks

Add a 'splitter' node to separate a bidirectional
packet flow into two unidirectional flows.

Part of a suite of nodes developed for packet flow control.
More to follow as I have time to port them to 5.x or
as others do so. The ipfw node will be the hardest..

Submitted by: "Vitaly V. Belekhov" <vitaly@riss-telecom.ru>