Add new _nl_category_name_idxs. Change all users. * locale/localeinfo.h: Adjust declaration of _nl_category_names. Declare _nl_category_name_idxs. * locale/findlocale.c: Adjust for _nl_category_names change. * locale/loadlocale.c: Likewise. * locale/newlocale.c: Likewise. * intl/dcigettext.c: Likewise.