trace-cmd: Add trace-cmd extract

This adds a way to extract a current trace into the data file.
That is, you can run a ftrace outside of trace-cmd, or use

 trace-cmd start  and   trace-cmd stop

to get a trace. Then to pull it into a file, use

  trace-cmd extract

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
1 file changed