add-patch: let options k and K roll over like j and J

add-patch: let options k and K roll over like j and J

Options j and J roll over at the bottom and go to the first undecided
hunk and hunk 1, respectively.  Let options k and K do the same when
they reach the top of the hunk array, so let them go to the last
undecided hunk and the last hunk, respectively, for consistency.  Also
use the same direction-neutral error messages.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>