complete ktap futex benchmark script
add trace_printk builtin function

trace_printk will print output into global tracing buffer of ftrace.

Get trace_printk output by:
	cat /sys/kernel/debug/tracing/trace_pipe

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
rename e.print_fmt to e.format
update highlights in README.md