Implemented a new "bt -c cpu(s)" option to display the backtrace
of the active task on one or more cpus.  The cpus must be specified
in a comma- and/or dash-separated list; for examples ""3", "1,8,9",
"1-23", or "1,8,9-14".  Similar to "bt -a", the option is only
applicable with crash dumps.
(atomlin@redhat.com)