add bench testsuite for ktap performance benchmark

first benchmarch is sembench for context switch(futex/wakeup, etc)

Using command: ./sembench -t 200 -w 20 -r 30 -o 2

Overhead of ktap interpreter is nearly 10%(or a little more)

Need optimize more

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
update doc: eventdef should be parsed in compiler

Eventdef maybe contain debuginfo(local variable, etc),
so it should be parsed in compiler, not interpreter.

And tracepoint/kprobe/uprobe should be unified in future.

future ktap script could be like below:

trace_begin func () {
        printf("trace start\n")
}

trace (p: @fs/read_write.c:285 file buf count) func (e) {
                printf("%d %d %x %s\n", cpu(), pid(), e.field(1), e.tostring())
}

trace_end func () {
        printf("trace end\n")
}

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>