code clean
add 3 functions definition, find_proc_node, find_pos_trace_node, and exist_trace_node, and modify spec of find_trace_node to parameters
add one more proc_list ptr
impl with test:add_proc_node, find_proc_node, exist_proc_node, print_proc_list. NMW:*_trace_* functions
add test for add_trace_node. NMW