Don’t assume CURRENT_TIME_LIST

Don’t assume CURRENT_TIME_LIST

Use timestamp accessors instead of delving into a timestamp
format that is planned to change in a future version.
* lisp/find-lisp.el (find-lisp-format-time):
* lisp/gnus/gnus-group.el (gnus-group-set-timestamp):
* lisp/gnus/gnus-icalendar.el (gnus-icalendar-show-org-agenda):
Use encode-time instead of delving into timestamp format.
* lisp/gnus/gnus-group.el (gnus-group-timestamp-delta):
Use float-time instead of delving into timestamp format.
* lisp/gnus/nnmaildir.el (nnmaildir-request-accept-article):
Use format-time-string instead of delving into timestamp format.
* lisp/gnus/nnmaildir.el (nnmaildir-request-expire-articles):
Use time-less-p instead of delving into timestamp format.
* lisp/ido.el (ido-wash-history, ido-file-name-all-completions):
Use time-equal-p instead of delving into timestamp format.
* lisp/net/tramp-adb.el (tramp-adb-handle-set-file-times):
Use format-time-string to generate POSIX ‘test -t’ format instead
of timestamp-format-dependent code along with shell arithmetic
that can’t possibly do the right thing on a POSIX platform.