• added "tag" option (BSD-style checksums) to shasum
  -- consistent with GNU sha1sum, sha224sum, etc.
  -- thanks to Christopher Tubbs for suggestion
  
• modified SHA.pm to use XSLoader
  -- falls back to DynaLoader if necessary
  
• decoupled Digest::SHA and Digest::SHA::PurePerl
  -- scripts/tests in each module now fully independent
  -- Digest::SHA::PurePerl to be phased out eventually
  -- past versions will remain available