Patch version 3:
 - add unit tests for code pages 932, 1252, CP_UTF7 and CP_UTF8
 - fix encode/decode flags for CP_UTF7/CP_UTF8
 - fix encode name on UnicodeDecodeError, support also "CP_UTF7" and "CP_UTF8" code page names

TODO:

 - The decoder (with errors) doesn't support multibyte characters, e.g. b"\xC3\xA9\xFF" is not correctly decoded using "replace" (insize is fixed to 1)
 - The encoder doesn't support surrogate pairs, but the result with UTF-8 looks correct
 - UTF-7 decoder is not strict, e.g. b'[+/]' is decoded to '[]' in strict mode
 - UTF-8 encoder is not strict, e.g. replace surrogates by U+FFFD
 - Use final in decode_mbcs_errors(): a multibyte character may be splitted between two chunks of INT_MAX bytes
 - Implement suggested Martin's optimizations?