bug#20316: 24.5; `string-lessp' doesn't respect value of LC_COLLATE

[Eli Zaretskii]

> From: Alexis <flexibeast@gmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>, michael.albinus@gmx.de
> Date: Tue, 14 Apr 2015 10:55:53 +1000
> 
>     So by default, Emacs sorts disregarding locale-specific ordering, 
> basically using the Unicode codepoints of the characters to order them. 
> 
> This makes sense given what you've said above, but can this still be referred 
> to as 'lexicographic' ordering? To me, 'lexicographic ordering' is ordering 
> as per a dictionary for the relevant language, not by codepoint for an 
> arbitrary encoding. Is this wrong?

I think we use "lexicographic" for lack of a more accurate word.  We
could use something like "code point (binary) order", but would that
be clear enough to be useful?

Note that we are not alone in this; at least this page:

  http://en.cppreference.com/w/cpp/string/byte/strcoll

says that the C function 'strcmp' does a "lexicographical comparison".
So do a few other similar pages; google for "difference between strcmp
and strcoll".

> One of the package's users had imported a set of contacts, then expected to 
> be able to sort those contacts according to Croatian rules, using `org-sort' 
> (from `org.el'). However, to quote the user, this resulted in the contacts 
> being sorted according to the English alphabet rules where the contact 
> entries which start with Croatian characters (Č,Ć,Đ,Š,Ž) are at the end of 
> the list, iow. after 'Z' entries, although it should go like this:
> 
> A,B,C,Č,Ć,D,Dž,Đ,..S,Š,..Z,Ž

That's "collation order" in action, note that the diacritic order is
applied _after_ the alphabetic order of the base characters.  That's
what string-collate-lessp does.