Telling HR staff about your stutter is the absolutely best thing we can do. And it helps the interviewer, too. I used to hire staff and it's really difficult to get candidates to be calm enough to answer questions enough so we can get the full measure of the person. A lot of people think interviewers are callous and cruel and dismissive and that's really not the case. Hiring people is expensive and time consuming and we want to get it right. Dismissing someone too nervous to deal well with an interview counterproductive. Being open and honest with hiring staff about your situation helps applicants in so many ways. Congratulations.