http_proxy.c: fix Connection token output to client
httpd: use comma_list_hdr() to output Transfer-Encoding
httpd.c: - properly truncate any existing telemetry log with auth creds
	 - also don't close/reopen telemetry log is userid hasn't changed
httpd: move content-encoding flags into txn.resp_body.enc rather than txn.flags.ce
httpd: completely buffer content-encoded static content rather than chunking it
http*.c: moved parsing of Range header into write_body() so we can handle range requests on Content-Encoded data
http_rss.c: Added Expires header for 410 (Gone) responses
getting ready for 2.4.17-caldav-beta6
http_rss.c: 410 (Gone) response shoul dbe cached for 1 year, not 1 hour