Use O_BINARY on Win32 when opening static files to serve via HTTP.

Otherwise the size reported by stat() may not match the number of bytes available to read(), as CRLF -> LF conversion happens.

See http://forum.flightradar24.com/threads/8358-DUMP1090-on-Windows-no-map-display-in-browser for the original report.

Untested! I have no Windows build environment.