Upgrade Digest-SHA from 5.87 to 5.88

  [DELTA]

        - added OUTPUT clause in SHA.xs to silence compiler warning
                -- ref. shaclose()
        - changed text file test (-T) to act on filehandles
                -- ref. addfile portable mode
                -- improves consistency when reading from STDIN
                -- still acts on filenames for early Perls (< 5.6)
        - added -M and -V options to shasum
                -- undocumented: for development and testing use only
Fix minor inaccuracy in the release manager's guide