(skeleton-pair-insert-maybe): Plain insert in Ovwrt mode

(skeleton-pair-insert-maybe): Plain insert in Ovwrt mode
(skeleton-insert): If skeleton doesn't fit in window, put beginning
at top before going to _ point.
(skeleton-internal-list): Rewritten so that resume: sections pertain
only to inferior skeletons and make str available there
(skeleton-read): Don't quit and remove partial skeleton when empty
string entered for outer iterator.  Added implicit argument `input'.
(define-skeleton, skeleton-insert, skeleton-internal-list): Use `x
rather than backquote's (` x) or own (list 'x)