Avoid unnecessary rounding errors in timestamps

Avoid unnecessary rounding errors in timestamps

Avoid the rounding errors of float-time when it’s easy.  E.g.,
replace (< (float-time a) (float-time b)) with (time-less-p a b).
* lisp/desktop.el (desktop-save):
* lisp/ecomplete.el (ecomplete-add-item):
* lisp/epg.el (epg-wait-for-completion):
* lisp/files.el (dir-locals-find-file, dir-locals-read-from-dir):
* lisp/image-dired.el (image-dired-get-thumbnail-image)
(image-dired-create-thumb-1):
* lisp/info.el (info-insert-file-contents):
* lisp/ls-lisp.el (ls-lisp-format-time):
* lisp/net/ange-ftp.el (ange-ftp-file-newer-than-file-p)
(ange-ftp-verify-visited-file-modtime):
* lisp/net/rcirc.el (rcirc-ctcp-sender-PING):
* lisp/textmodes/remember.el (remember-store-in-mailbox):
* lisp/url/url-cookie.el (url-cookie-expired-p):
Bypass float-time to avoid rounding errors.

* lisp/files.el (dir-locals-find-file):