Tim Kientzle 5a57a7f095 Clean up usage message(s):
* Usage goes to stderr, not stdout
  * Use correct argument markup
  * bsdtar --help  no longer exits with an error return code
  * ensure that the word "bsdtar" appears in the first
    line output from "bsdtar --help" (even if the program is
    invoked as "tar")

In particular, scripts can now test for the presence of bsdtar.
For example, in /bin/sh:

if (tar --help 2>&1 | grep bsdtar >/dev/null 2>&1) then \
          echo bsdtar; else echo not bsdtar; fi
2004-06-15 00:07:23 +00:00
..
2004-06-15 00:07:23 +00:00