perf data ctf: Prepare collect non-sample events

Following commits are going to allow 'perf data convert' to collect not
only samples, but also non-sample events like comm and fork. In this
patch we count non-sample events using c.non_sample_count, and prepare
to print number of both type of events like:

  # ~/perf data convert --all --to-ctf ./out.ctf
  [ perf data convert: Converted 'perf.data' into CTF data './out.ctf' ]
  [ perf data convert: Converted and wrote 0.846 MB (6508 samples, 686 non-samples) ]

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1466767332-114472-5-git-send-email-wangnan0@huawei.com


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