Parses and loads the source s, which can be a File, InputStream or String naming a URI. Returns a tree of the xml/element struct-map, which has the keys :tag, :attrs, and :content. and accessor fns tag, attrs, and content. Other parsers can be supplied by passing startparse, a fn taking a source and a ContentHandler and returning a parser. Prior to 1.11, used startparse-sax by default. As of 1.11, uses startparse-sax-safe, which disables XXE (XML External Entity) processing. Pass startparse-sax to revert to prior behavior.