Log Message:
Changes 5.62:
* removed unnecessary loading of MIME::Base64 module

Changes 5.61:
* corrected bug in 'algorithm' method
* fixed -x option in Makefile.PL
  -- not often used since it deliberately excludes all 64-bit SHA transforms
* addressed minor documentation oversights

Changes 5.60:
* added new SHA-512/224 and SHA-512/256 transforms
  -- ref. NIST Draft FIPS 180-4 (February 2011)
* simplified shasum by removing duplicative text
* improved efficiency of Addfile
  -- expensive -T test now occurs only in portable mode

Changes 5.50:
* adopted convention that '-' always means STDIN
  -- actual filename '-' accessed as './-'
  -- accords with behavior of sha1sum/md5sum
* corrected undefined subroutine oversight in shasum
  -- inadvertent migration of _bail() from SHA.pm