Issue #12892: The utf-16* and utf-32* codecs now reject (lone) surrogates. The utf-16* and utf-32* encoders no longer allow surrogate code points (U+D800-U+DFFF) to be encoded. The utf-32* decoders no longer decode byte sequences that correspond to surrogate code points. The surrogatepass error handler now works with the utf-16* and utf-32* codecs. Based on patches by Victor Stinner and Kang-Hao (Kenny) Lu.