* Decode thousands separator and decimal point using PyUnicode_DecodeLocale()
(from the locale encoding), instead of decoding them implicitly from latin1
* Remove _PyUnicode_InsertThousandsGroupingLocale(), it was not used
* Change _PyUnicode_InsertThousandsGrouping() API to return the maximum
character if unicode is NULL
* Replace MIN/MAX macros by Py_MIN/Py_MAX
* stringlib/undef.h undefines STRINGLIB_IS_UNICODE
* stringlib/localeutil.h only supports Unicode
ucs1, ucs2 and ucs4 libraries have to scan created substring to find the
maximum character, whereas it is not need to ASCII strings. Because ASCII
strings are common, it is useful to optimize ASCII.