Switching SEXP_USE_SEND_FILE to a whitelist for BSD and Linux, instead of a blacklist.  Fixes issue #192.
Switching SEXP_USE_SEND_FILE to a whitelist for BSD and Linux,
instead of a blacklist.  Fixes issue #192.

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