Writing stat round events on 'perf stat record' for each interval round.
In non interval mode we store round event after the last stat event.

Committer note:

After the patch:

  $ perf report -D | grep PERF_RECORD | grep ROUND
  0x852 [0x18]: PERF_RECORD_STAT_ROUND
  $
Reported-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1446734469-11352-9-git-send-email-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>