o Implement -c (clear) to clear previously kept headers (note that
dumps not cleared will remain until -c is used),
o Implement -f (force) to allow re-saving a previously saved dump,
o Implement -k (keep) and make clearing the dump header the default,
o Implement -v (verbose) and make most output conditional upon it,
o Emit minimal output for the non-verbose case with the assumption
that savecore is run mostly from within /etc/rc,
o Update usage message to reflect what is and what's not,
o mark -d as obsolete.
Low-level changes:
o Rename devname to device, for devname mirrors a global declaration
and GCC 3.x warns about it,
o Open the dump device R/W for clear and !keep to work,
o Reorder the locals of DoFile according to style(9),
o Remove newlines from strings passed to warn* and err*,
o Use stat(2) to check if a dump has been saved before,
o Truncate existing core and info files to support force,
o First check for the magic and the version before we complain about
parity errors. This prevents emitting parity error messages when
there's no dump,
o Keep track of the number of headers found and the number of headers
saved to support the minimal output,
o Close files we opened in DoFile. Not critical, but cleaner.
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