Fix ABI compat shims for FreeBSD 9.0-9.1 binaries (CAM_VERSION 0x16).

This is a direct commit to stable/10, inspired by some commits to later
branches.

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

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

Re-do r255853. Along with adding back the API/ABI changes from the
original, this hides the contents of cam_compat.h from ktrace/kdump/truss,
avoiding problems there. There are no user-servicable parts in there, so
no need for those tools to be groping around in there.

Approved by: re

Revert r255853 pending fixes to build errors in usr.bin/kdump

Approved by: re (implicit)

Update the CAM API for FreeBSD 10:

- Remove the timeout_ch field. It's been deprecated since FreeBSD 7.0;
MPSAFE drivers should be managing their own timeout storage. The
remaining non-MPSAFE drivers have been modified to also manage their own
storage, and should be considered for updating to MPSAFE (or removal)
during the FreeBSD 10.x lifecycle.

- Add fields related to soft timeouts and quality of service, to be used
in upcoming work.

- Add room for more flags in the CCB header and path_inq structures.

- Begin support for extended 64-bit LUNs.

- Bump the CAM version number to 0x18, but add compat shims. Tested with
camcontrol and smartctl.

Reviewed by: nathanw, ken, kib
Approved by: re
Obtained from: Netflix

Fix an unfortunate typo with the compat shims

Obtained from: Netflix
MFC after: now

Add infrastructure for doing compatibility shims, as has been sorely
needed for the last 10 years. Far too much of the internal API is
exposed, and every small adjustment causes applications to stop working.
To kick this off, bump the API version to 0x17 as should have been done
with r246713, but add shims to compensate. Thanks to the shims, there
should be no visible change in application behavior.

I have plans to do a significant overhaul of the API to harnen it for
the future, but until then, I welcome others to add shims for older
versions of the API.

Obtained from: Netflix