New operation :custom-standard-value.

New operation :custom-standard-value.
(Custom-reset-standard): Use it.
(custom-variable, custom-face): Define it.
(custom-variable-standard-value, custom-face-standard-value): New fns.
(custom-face-save): Don't save a face whose value is standard.
(custom-save-faces): Use SYMBOL, not 'default, to set NOW and COMMENT.

(custom-face-edit-fix-value): If VALUE is not a list, pass it thru.