Miscellanious features and adjustments to cpdup.

Miscellanious features and adjustments to cpdup.

* Add the -V option to cpdup.  If specified cpdup will verify the contents
  of regular files which otherwise appear to be the same.

* Only MD5 regular files.

* Separate out target bytes read from source bytes read, and do not count
  the stat structure as bytes read.

* Track the number of hard-links created and report in -I output.