Adding sexp_bytes_maybe_null_data macro for bytevector FFI support.
Adding sexp_bytes_maybe_null_data macro for bytevector FFI support.

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