Update Digest-SHA to CPAN version 5.50

Update Digest-SHA to CPAN version 5.50

  [DELTA]

  5.50  Tue Dec 14 06:20:08 MST 2010
        - 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