bug#18051: [Emacs-diffs] trunk r117726: Add string collation.

[Paul Eggert]

A couple more things.

First, the current algorithm looks only at LC_COLLATE, but the usual 
approach is to default LC_COLLATE to LANG if LC_COLLATE isn't set, and 
to have LC_ALL override LC_COLLATE.  Shouldn't Emacs take a similar 
approach, for compatibility?

More generally, it strikes me that string-collate-lessp will be quite 
slow due to the overhead of looking up the locale environment string and 
creating and destroying a locale for each string comparison.  Instead, 
shouldn't Emacs should have a locale object that the Emacs Lisp 
programmer can create, an object that encapsulates the low level 
locale_t object, and which can be passed as an optional argument to 
string-collate-lessp?  That way, string-collate-p would never have to 
inspect the environment itself, or to create or destroy a locale.