bug#22483: 25.1.50; Doc string of `isearch-lax-whitespace' does not show toggle key

[Drew Adams <drew.adams@oracle.com>]

> > The doc string says you can toggle using command
> > `isearch-togggle-lax-whitespace'.  That's pretty useless, as it makes
> > sense only during Isearch.
> 
> Not true, it makes sense outside of Isearch as well (toggles the
> default).

Interesting.  I thought this was a user option, but I see now that
it is not.  (I know that vanilla Emacs refuses to let users toggle
an option during Isearch, even though that lets them perform
subsequent searches also using the new value.)

So why does the toggle command initiate search as well?  And if
that is by design and not a bug, perhaps it should be documented
as part of the command behavior (it does not just toggle the
variable value).

`M-x isearch-lax-whitespace' starts searching backward, with this
message:

  Pending literal I-search backward:

Oh, and that happens each time I "toggle" the value.  The value
changes (correctly), but the search initiated always shows that
backward-literal-search message.