Rewrite of the CAM error recovery code.

Rewrite of the CAM error recovery code.

Some of the major changes include:

	- The SCSI error handling portion of cam_periph_error() has
	  been broken out into a number of subfunctions to better
	  modularize the code that handles the hierarchy of SCSI errors.
	  As a result, the code is now much easier to read.

	- String handling and error printing has been significantly
	  revamped.  We now use sbufs to do string formatting instead
	  of using printfs (for the kernel) and snprintf/strncat (for
	  userland) as before.

	  There is a new catchall error printing routine,
	  cam_error_print() and its string-based counterpart,
	  cam_error_string() that allow the kernel and userland
	  applications to pass in a CCB and have errors printed out
	  properly, whether or not they're SCSI errors.  Among other
	  things, this helped eliminate a fair amount of duplicate code
	  in camcontrol.

	  We now print out more information than before, including
	  the CAM status and SCSI status and the error recovery action
	  taken to remedy the problem.

Obtained-from: FreeBSD