(mark-sexp-diary-entries): Retrieve mark
from diary-sexp-entry and pass it to mark-visible-calendar-date.
(list-sexp-diary-entries): Update doc string for new docs for ....
If diary-sexp-entry returns a cons, only add the text to the diary list.
(diary-sexp-entry): Allow sexps to return a cons of the form (MARK
. STRING) to specify what face or character mark should be used in
the calendar display.
(diary-date, diary-block, diary-float, diary-anniversary)
(diary-cyclic): Add optional MARK parameter, specifying what face
or character to use in the calendar display. These will now
return (MARK . ENTRY).