How involved do you want to get? If these break off flush then you have a job ahead of you. I have successfully removed one using this method. First get a dremel tool with a very tiny routing bit. They make them real tiny, smaller than a pin head. Wear your safety glasses and then cut into the exposed flush end of the stub by working it back and forth cutting a slot the best you can. Try to make it look like a screw head slot. I recommend doing this from the back end of the dropout. Next, if you have or have access to a small ultra-sonic cleaning tub, set your dropout such that it is pointing down in a solution of kerosene inside of the U-S cleaning tub. Turn it on a let it go for a couple of hours. If you have a heated tub then turn that on low. After that, let it cool but keep it pointed downward. Now take a tiny jewelers screwdriver and see if you can back it our ever so slowly. Even if you just get it out an eighth of an inch, that is enough to put a vise grip on it and finish the job.