http_dav.c: allow a precondition error code to be passed to xml_add_response along with a status code
http_client.h: don't share the same flag value for BODY_CONTINUE (request) and BODY_CLOSE (response) as it causes confusion in http_read_body()
httpd.c: use an absolute URL for .well-known redirects
http_ischedule.c: properly set Originator based on component type and method; properly handle redirects after receiver closes connection
http_ischedule.c: better way of determining Originator in isched_send()
http_caldav.c: don't send POLLSTATUS to VOTER that triggered the POLLSTATUS