hgweb: fix broken URLs of RSS/Atom feeds (issue1772) This fixes doubled URL, e.g. http://example.orghttp://example.org/..., which appears on RSS/Atom feeds served by hgwebdir. It splits baseurl to update SERVER_NAME, SERVER_PORT and SCRIPT_NAME, according to RFC 3875. Updated the test output since SCRIPT_NAME becomes not to contain http://host:port part.