perf probe: Show trace event definition

Add --definition/-D option for showing the trace-event definition in
stdout. This can be useful in debugging or combined with a shell script.

e.g.
  ----
  # perf probe --definition 'do_sys_open $params'
  p:probe/do_sys_open _text+2261728 dfd=%di:s32 filename=%si:u64 flags=%dx:s32 mode=%cx:u16
  ----

Suggested-and-Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/147214226712.23638.2240534040014013658.stgit@devbox


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>