fixing srfi-27 support for systems with posix rand_r but not random_r
fixing srfi-27 support for systems with posix rand_r but not random_r

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