bug#29838: 26.0; Elisp manual: describe standard-error sexps

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

> > If users never saw such messages then perhaps there
> > would be no need to describe such things as
> > `(args-out-of-range 9 9)'.  If they saw only nice
> > error messages such as "Args out of range: [1 2 3 4], -1"
> > then there would be no such problem.
> 
> Is "Args out of range: 9, 9" any more informative?

Of course not.  But that's not the corresponding
error message, is it?

Now that you bring that up, I don't see any good
description of the error message itself, either.
So yes, that's perhaps the first thing to fix.

Ideally the message should be self-explanatory,
and should indicate what the range is that the
specified args fall outside of.