Rename TIME->HTTP-DATE-STRING to RFC822-TIME->STRING.

(Missed by sperber, noticed by bernauer.)

scheme/httpd/file-dir-handler.scm

@@ -443,7 +443,7 @@
 				   '())
 			       (list
 				(cons 'last-modified
-				      (time->http-date-string
+				      (rfc822-time->string
 				       (file-info:mtime info)))
 				(cons 'content-length (file-info:size info))))
 		       (make-writer-body

scheme/packages.scm

@@ -671,6 +671,7 @@
 	htmlout
 	crlf-io
 	(subset srfi-13 (string-join))
+	(subset rfc822 (rfc822-time->string))
 	sunet-utilities			; dotdot-check, copy-inport->outport
 	conditions
 	handle-fatal-error