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
Update head/ to -ALPHA3.
This commit marks the point the final KBI change was made as part of the
10.0-RELEASE cycle.

Approved by:	re (implicit)
Sponsored by:	The FreeBSD Foundation
Improve error handling in the old initiator, preventing panic on attempt
to load iscsi_initiator.ko when iscsi.ko is already loaded.

Approved by:	re (glebius)
Sponsored by:	FreeBSD Foundation