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

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

Add card_if.h and pccarddevs.h

Let modules use the kernel's opt_*.h files if built along with
the kernel by wrapping all targets for fake opt_*.h files in
.if defined(KERNBUILDDIR). Thus, such fake files won't be
created at all if modules are built with the kernel.

Some modules undergo cleanup like removing unused or unneeded
options or .h files, without which they wouldn't build this way
or the other.

Reviewed by: ru
Tested by: no binary changes in modules built alone
Tested on: i386 sparc64 amd64

Remove bridge(4) from the tree. if_bridge(4) is a full functional
replacement and has additional features which make it superior.

Discussed on: -arch
Reviewed by: thompsa
X-MFC-after: never (RELENG_6 as transition period)

Use a consistent style and one much closer to the rest of /usr/src

Added NEC PC-9801-83, 84, PC-9801-103, 104, PC-9801N-25 and PC-9801N-J02R
support which use National Semiconductor DP8393X (SONIC) as ethernet
controller. Currently, this driver is used on only PC-98.

Submitted by: Motomichi Matsuzaki <mzaki@e-mail.ne.jp>
Obtained from: NetBSD/pc98