fixing bug when reading invalid "." in non-decimal bignums (issue 32)
fixing bug when reading invalid "." in non-decimal bignums (issue 32)

holmescn/chibi-scheme,norton/chibi-scheme,holmescn/chibi-scheme,norton/chibi-scheme,norton/chibi-scheme,norton/chibi-scheme,holmescn/chibi-scheme,holmescn/chibi-scheme,holmescn/chibi-scheme,norton/chibi-scheme,norton/chibi-scheme