f1d0fbbdf4 allowed customizing the .
mapping by making the implementation function publicly accessible. Let's
do the same to s:wrap(), so that the other mappings (u, U, <C-R>) can be
extended, too.
(Personally, I'd like to have undo / redo stop and beep at the last
saved position, to avoid that I accidentally undo beyond the saved state
even though I didn't intend to.)
8ee7450812