bug#22104: 25.1.50; doc string of `modify-frame-parameters'

[Eli Zaretskii]

> Date: Mon, 7 Dec 2015 10:07:49 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: 22104@debbugs.gnu.org
> 
> I think that statement can just be removed.

I believe this feature is used to make "frame-local" variables.  So
removing that sentence will lose information.

> No one would guess that any special, additional action would be
> undertaken for a parameter that Emacs does not recognize.

But it could well barf for such a parameter, at least in principle.
So that sentence does add useful information.

> It is important to say that users can add their own parameters.
> 
> And I guess it is helpful to add that Emacs does not do anything
> with them (unless the user programs it to do so).  But if we can't
> do that without confusing readers more, then this addition should
> be dropped, IMO.

Oh, I think we have all the technology necessary to say that in a way
that won't confuse users.