Remove or re-work support for the several features from the past:
- remove incomplete support for trimming slice/partition names
- remove mapping from old device names "sd" and "st"
- remove whitespace trimming
- remove unconditional skipping of leading 'r' in a device name
- skip leading 'n' or 'e' only if the following device name matches
a list of known devices that support no-rewind and eject-on-close
features; currently this is only sa(4)
- reflect the above changes in comments in code and in cam(3)
- remove a note cautioning against use of cam_get_device and
cam_open_device in cam(3)
Reviewed by: mjacob
5bcc8fafda