Correct ses-rename-cell cursor-intangible text prop updating.

Correct ses-rename-cell cursor-intangible text prop updating.

There were two problems:

- First ses-rename-cell has to work when called non interactively
  (with non-nil CELL argument), so in this case the start pos of
  put-text-property cannot be plainly (point), you need a
  ses-goto-print call before

- Second, the range itself was computed erronously, only the first
  char was affected instead of the full cell width. This was not
  noticeable prior to changes (Deprecate `intangible' and
  `point-entered' properties) made by Stefan on 2015-04-13T19:51:15Z

* lisp/ses.el (ses-rename-cell): Correct computation of position range
to which the 'cursor-intangible text property has to be set to cell
new name.