iswspace, iswxdigit.
- Fixed RtlInt64ToUnicodeString and RtlIntegerToUnicodeString.
- According to tests RtlAppendUnicodeStringToString leaves the
  destination unchanged when the source length is 0 (FIXED).
- Documentation updates in RtlExtendedMagicDivide,
  RtlLargeIntegerToChar, RtlInt64ToUnicodeString, RtlUpperChar,
  RtlUpperString, RtlUpcaseUnicodeChar, RtlCharToInteger,
  RtlIntegerToChar, RtlUnicodeStringToInteger,
  RtlIntegerToUnicodeString, _ultoa, _ltoa, _itoa, _ui64toa, _i64toa,
  _atoi64, _ultow, _ltow, _itow, _ui64tow, _i64tow, _wtol, _wtoi,
  _wtoi64.