resolve

Where entry, an address a playlist at base names, points: an address beside a list on a server resolved as RFC 3986 says, and a path beside a list on disk, as parse resolves every entry. An address with a scheme of its own stands, except a file:// one, which becomes the path it names. For a caller that reads a playlist parse does not, such as an HLS master playlist whose backup variants it wants to open (#440).