bug#26925: Improve /doc/lispref/strings.texi (split-string) documentation

[Jean-Christophe Helary]

> On 2017/06/04, at 22:57, Eli Zaretskii <eliz@gnu.org> wrote:
> 
> Frankly, I think we are splitting hair, but anyway...

*You* are splitting hairs. If I had made that modification in the first patch I 
sent we would never be having this conversation.

If you don't want to see that string change, just say so and I'll drop it.

>> And btw, the docstring of `split-string' does not speak about TRIM as
>> "optional argument" either.
> 
> Which is a mistake, IMO, because the doc string uses neither of the
> above 2 patterns, and so makes it sound like these arguments are not
> optional at all.

No, because in the function signature they are defined as optional. If people 
go as far as checking the doc string, they at least take a look at the function 
signature. There is no ambiguity there at all.

Jean-Christophe