Don't warn on toggle-read-only calls.

Don't warn on toggle-read-only calls.

Clarify the documentation of toggle-read-only, and audit the code tree
for uses of toggle-read-only; where appropriate, switch to setting the
variable buffer-read-only or calling toggle-read-only with a (new)
second arg.

* lisp/files.el (toggle-read-only): Doc fix and code cleanup.  New arg
to allow printing the message when called from Lisp.

* lisp/emacs-lisp/bytecomp.el (byte-compile-interactive-only-functions):
Remove toggle-read-only.

* lisp/bindings.el (mode-line-toggle-read-only):
* lisp/dired.el (dired-toggle-read-only):
* lisp/ibuffer.el (ibuffer-do-toggle-read-only): Call toggle-read-only
with non-nil second arg.

* lisp/bs.el (bs-toggle-readonly):
* lisp/buff-menu.el (Buffer-menu-toggle-read-only): Remove
with-no-warnings around toggle-read-only.

* lisp/ffap.el (ffap--toggle-read-only): Accept a list of buffers.
Remove with-no-warnings around toggle-read-only.
(ffap-read-only, ffap-read-only-other-window)
(ffap-read-only-other-frame): Callers changed.

* lisp/help-mode.el: Don't require view package.
(help-mode-finish): Set buffer-read-only instead of calling
toggle-read-only.

* lisp/emacs-lisp/eieio-custom.el (eieio-customize-object):
* lisp/vc/ediff.el (ediff-set-read-only-in-buf-A): Set buffer-read-only
directly.

* lisp/gnus/smime.el (smime-certificate-info): Set buffer-read-only directly,
instead of calling toggle-read-only with a (bogus) argument.

* doc/emacs/buffers.texi (Misc Buffer): Document view-read-only.

* doc/lispref/buffers.texi (Read Only Buffers): Document toggle-read-only
changes.  Reword to account for the fact that read-only is currently not
supported in overlay properties.