gb_to_iso
n = gb_to_iso(st->_lastc, **inbuf, *outbuf, *outbytesleft);
n = gb_to_iso(st->_lastc, **inbuf, *outbuf, *outbytesleft);
int gb_to_iso(char in_byte1, char in_byte2, char *buf, int buflen);
n = gb_to_iso(st, *outbuf, *outbytesleft);
int gb_to_iso(_iconv_st * st, char* buf, int buflen);