* lisp/emacs-lisp/vtable.el (vtable--insert-header-line): Don't
insert the divider at the end.
(vtable-narrow-current-column, vtable-widen-current-column): Don't
error out when being called on the divider.
* doc/misc/vtable.texi (Making A Table): Document it.
* lisp/emacs-lisp/vtable.el (vtable): Add a divider slot.
(make-vtable): Accept :divider and :divider-width arguments.
(vtable--insert-line, vtable--insert-header-line): Display the
divider.
* doc/misc/vtable.texi (Making A Table): Document it.
* lisp/emacs-lisp/vtable.el (vtable): Add :row-colors.
(make-vtable): Ditto.
(vtable--compute-colors, vtable--color-blend): New functions.
(vtable--insert-line): Take a line number argument and adjust
callers.
* doc/misc/vtable.texi (Making A Table): Document it.
* lisp/emacs-lisp/vtable.el (vtable): Add a column color element.
(make-vtable): Use it.
(vtable--insert-line): Insert the colors here.
