perf evsel: Support printing callchains with arrows

perf evsel: Support printing callchains with arrows

The EVSEL__PRINT_CALLCHAIN_ARROW options can be used to print callchains
with arrows for readability.  It will be used 'sched timehist' command
like below:

    __schedule <- schedule <- schedule_timeout <- rcu_gp_kthread <- kthread <- ret_from_fork
    __schedule <- schedule <- schedule_timeout <- rcu_gp_kthread <- kthread <- ret_from_fork
    __schedule <- schedule <- worker_thread <- kthread <- ret_from_fork

Suggested-and-Acked-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/20161116060634.28477-3-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>