[HEADSUP] changes to cam_get_device() and cam_open_device()

As there was no objections, I am going to commit changes to cam_get_device()
that remove the following features:

- ignoring 'r' and 'n' at the start of device name
- ignoring whitespace at end of device name
- parsing and ignoring slice and partition names in a device name

cam(3) manual page is going to be updated to reflect the changes.
This would simplify the code and disambiguate its behavior.

Non-rewound and character disk/SCSI devices has not been supported for quite a
while now.  Support for parsing partition/slice names is incomplete (e.g. GPT
scheme is not supported) and of questionable usefulness.

Full diff is here:
http://people.freebsd.org/~avg/cam.diff

If you know of any functionality or application that would be broken by this
change please stop me ASAP.
Also, if you have any other reason to object to the change please speak up
before the change is committed.

Thank you.

-- 
Andriy Gapon