bug#1434: Docstring for `toggle-read-only' shouldn't imply the buffer is file-visiting

[Glenn Morris]

"Juanma Barranquero" wrote:

> `toggle-read-only' is useful for non-visiting buffers too, though
> the docstring seems to imply otherwise.

So let's change it?

*** files.el    3 Dec 2008 03:26:01 -0000       1.1022
--- files.el    3 Dec 2008 23:57:40 -0000
***************
*** 4404,4412 ****
    (set-buffer-modified-p arg))
  
  (defun toggle-read-only (&optional arg)
!   "Change whether this buffer is visiting its file read-only.
  With prefix argument ARG, make the buffer read-only if ARG is
! positive, otherwise make it writable.  If visiting file read-only
  and `view-read-only' is non-nil, enter view mode."
    (interactive "P")
    (if (and arg
--- 4404,4412 ----
    (set-buffer-modified-p arg))
  
  (defun toggle-read-only (&optional arg)
!   "Change whether this buffer is read-only.
  With prefix argument ARG, make the buffer read-only if ARG is
! positive, otherwise make it writable.  If buffer is read-only
  and `view-read-only' is non-nil, enter view mode."
    (interactive "P")
    (if (and arg