wind_ucs2utf8
ret = wind_ucs2utf8(bmp, bmplen, ss, NULL);
ret = wind_ucs2utf8(ucs2, ucs2len, s, &u8len);
return wind_ucs2utf8(in, in_len, NULL, out_len);
int wind_ucs2utf8(const uint16_t *, size_t, char *, size_t *);