• added new capabilities to the "addfile" method
  -- now able to accept file names as well as handles
  -- includes mode for portable digest calculation
  -- thanks to Adam Kennedy for emails and ideas
  ref. File::LocalizeNewlines
  
• used expanded addfile interface to simplify shasum (sumfile)
  -- regex a tad less general than 5.37, but handles all
  known newline variants in UNIX/Windows/MacOS
  
• enhanced WARNING messages from shasum checkfile processing
  -- to mimic behavior of md5sum