* lisp/rect.el: Make it possible to move bounds past EOL or into TABs.

* lisp/rect.el: Make it possible to move bounds past EOL or into TABs.
(operate-on-rectangle): Use apply-on-rectangle.
(rectangle--mark-crutches): New var.
(rectangle--pos-cols, rectangle--col-pos, rectangle--point-col)
(rectangle--crutches, rectangle--reset-crutches): New functions.
(apply-on-rectangle): Obey crutches.  Avoid setq.
Fix missing final iteration if end is at EOB&BOL.
(rectangle-mark-mode-map): Add remap bindings for
exchange-point-and-mark and char/line movements.
(rectangle--*-char): New function.
(rectangle-exchange-point-and-mark, rectangle-right-char)
(rectangle-left-char, rectangle-forward-char)
(rectangle-backward-char, rectangle-next-line)
(rectangle-previous-line): New commands.
(rectangle--place-cursor): New function.
(rectangle--highlight-for-redisplay): Use it.  Use apply-on-rectangle.