bug#25744: make dd quiet except for warnings and errors

[積丹尼 Dan Jacobson]

man dd
‘status=LEVEL’
     Transfer information is normally output to stderr upon receipt of
     the ‘INFO’ signal or when ‘dd’ exits.  Specifying LEVEL will adjust
     the amount of information printed, with the last LEVEL specified
     taking precedence.

     ‘none’
          Do not print any informational or warning messages to stderr.
          Error messages are output as normal.

     ‘noxfer’
          Do not print the final transfer rate and volume statistics
          that normally make up the last status line.

$ dd if=/dev/null
0+0 records in
0+0 records out
0 bytes copied, 0.00415153 s, 0.0 kB/s
$ dd if=/dev/null status=noxfer
0+0 records in
0+0 records out
$ dd if=/dev/null status=none
$

I like the final one, except I don't want to miss warnings. So please add a
     ‘quiet'
          Do not print any informational messages to stderr.
          Warning and error messages are output as normal.