scripts to format function traces

There is a nice script in kernel scripts/draw_functrace.py

it can draw function traces without using graph_function type built-in tracing.

# echo function > /sys/kernel/debug/tracing/current_tracer
$ cat /sys/kernel/debug/tracing/trace_pipe > ~/raw_trace_func
$ scripts/draw_functrace.py < raw_trace_func > draw_functrace