Created attachment 131801 [details] [review]
Fix as Git commit (obtained with 'git format-patch)

As reported at https://lists.freedesktop.org/archives/fontconfig/2017-June/005940.html :

FcLangSetIndex() contains code like this:

  low = fcLangCharSetRanges[firstChar - 'a'].begin;
  high = fcLangCharSetRanges[firstChar - 'a'].end;
  /* no matches */
  if (low > high)

The assumption behind this test didn't hold before the attached
commit/patch, unless there is at least one language name that starts
with 'z' (which is thankfully the case in our world :-). If the last
language name in lexicographic order starts for instance with 'x',
this change ensures that fcLangCharSetRanges['y' - 'a'].begin and
fcLangCharSetRanges['z' - 'a'].begin are equal to NUM_LANG_CHAR_SET,
in order to make the above assumption correct in all cases.