FcLangSetHasLang - test langset for language support
#include <fontconfig/fontconfig.h>
FcLangResult FcLangSetHasLang (const FcLangSet *ls, const FcChar8 *lang);
FcLangSetHasLang checks whether ls supports lang. If
  ls has a matching language and territory pair, this function returns
  FcLangEqual. If ls has a matching language but differs in which
  territory that language is for, this function returns
  FcLangDifferentTerritory. If ls has no matching language, this function
  returns FcLangDifferentLang.