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

Style cleanup.

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

Major update to the 'twe' driver.

- Layout reorganisation to enhance portability. The driver now has
a relatively MI 'core' and a FreeBSD-specific layer over the top.
Since the NetBSD people have already done their own port, this is
largely just to help me with the BSD/OS port.

- Request ID allocation changed to improve performance (I'd been
considering switching to this approach after having failed to come
up with a better way to dynamically allocate request IDs, and seeing
Andy Doran use it in the NetBSD port of the driver convinced me
that I was wasting my time doing it any other way). Now we just
allocate all the requests up front.

- Maximum request count bumped back to 255 after characterisation
of a firmware issue (off-by-one causing it to crash with 256
outstanding commands).

- Control interface implemented. This allows 3ware's '3dm' utility to
talk to the controller. 3dm will be available from 3ware shortly.

- Controller soft-reset feature added; if the controller signals a
firmware or protocol error, the controller will be reset and all
outstanding commands will be retried.

Fixed style bugs that I unfortunately noticed because bsd.kmod.mk was
being reconstructed.

Use .include <bsd.kmod.mk> to get to ../../*/conf/kmod.mk instead of
encoding the relative path.

Some joker decided to make it even harder to build modules outside the
kernel, and rather than fix the make search path, hardcoded it into the
module Makefiles themselves. Go with the herd.

Add the 'twe' driver module makefile.