perf report: Add --hierarchy option

The --hierarchy option is to show output in hierarchy mode.  It extends
folding/unfolding in the TUI and GTK browsers to support sort items as
well as callchains.  Users can toggle the items to see the performance
result at wanted level.

  $ perf report --hierarchy --tui
   Overhead       Command / Shared Object / Symbol
  --------------------------------------------------
  +  32.96%       gnome-shell
  -  15.11%       swapper
     -  14.97%       [kernel.vmlinux]
           6.82%        [k] intel_idle
           0.66%        [k] menu_select
           0.43%        [k] __hrtimer_start_range_ns
  ...

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1456326830-30456-17-git-send-email-namhyung@kernel.org


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