From Scott Lamb: * Allow the user to set the Content-Length: then stream a reply. This is useful for large requests of a known size. Added unit test. * Don't send a response body on HEAD requests, 1xx status codes, 204 status codes, or 304 status codes, as described in RFC 2616 section 4.3. (Doing otherwise causes problems - in particular, if a 304 has a chunked body (even an empty one), Safari 3.1.1 issues and then fails the next request on the connection with the non-sequitur error message "Too many HTTP redirects"!) * Specify a default Content-Type: when a response body is required, not when we have data in the response buffer by the time we make the header. (I.e., do this on evhttp_send_reply_start() for consistency.) * Don't expect a body in response to HEAD requests. svn:r898