sum manpage in coreutils-5.2.1-48.1 minor fixups

[root]

the info page is right, but might as well fix up the man page since it
is so short and it had us confused:

       -r     defeat -s, use BSD sum algorithm, use 1K blocks

       -s, --sysv
              use System V sum algorithm, use 512 bytes blocks

would be clearer if it just said:

       -r     use BSD sum algorithm, use 1K blocks (the default)

       -s, --sysv
              use System V sum algorithm, use 512 bytes blocks
                                                      ^---- might as well 
remove this "s"


or just use the exact same verbage as info page:

   By default, GNU `sum' computes checksums using an algorithm
compatible with BSD `sum' and prints file sizes in units of 1024-byte
blocks.

   The program accepts the following options.  Also see *Note Common
options::.

`-r'
     Use the default (BSD compatible) algorithm.  This option is
     included for compatibility with the System V `sum'.  Unless `-s'
     was also given, it has no effect.

`-s'
`--sysv'
     Compute checksums using an algorithm compatible with System V
     `sum''s default, and print file sizes in units of 512-byte blocks.