add FILE and DIR types to highlight list

I was gonna also add all the stdint types but there's too many, would there be any major conflicts by just highlighting anything that ends with _t? I don't know how to do that in this regex impl anyway tho. Also would it be possible to highlight all functions by just checking for a word followed by opening and closing parenthesis? Would be a lot nicer then just highlighting a few hardcoded common libc functions.