[PATCH v2] Improve fnmatch performance.

[Paul Eggert]

Ondřej Bílka wrote:
> How to synchronize this with gnulib? Only implementation specific detail
> is utf8 detection.

It could be something like this:

  #if _LIBC
   struct __locale_data *current = _NL_CURRENT_LOCALE->__locales[LC_COLLATE];
   uint_fast32_t encoding =
     current->values[_NL_ITEM_INDEX (_NL_COLLATE_ENCODING_TYPE)].word;
   bool is_utf8 = encoding == !__cet_other;
  #else
   bool is_utf8 = STRCASEEQ (locale_charset (),
                             "UTF-8", 'U','T','F','-','8',0,0,0,0)
  #endif

We should package this sort of thing up and make it easier to use, but that 
could be another day.