* calendar/time-date.el (autoload):
Expand define-obsolete-function-alias into defalias and make-obsolete
for old Emacsen that Gnus supports.
(with-no-warnings): Define it for old Emacsen.
(time-to-seconds): Don't use (featurep 'xemacs) to check if float-time
is available.
(time-to-number-of-days): Don't use (featurep 'xemacs) to check if
float-time is available; suppress compile warning for time-to-seconds.