[util] Use O_BINARY instead of _O_BINARY

The latter doesn't seem to be available in Cygwin.  I'm surprised it
compiled before...

util/options.cc

@@ -490,7 +490,7 @@ font_options_t::get_font (void) const
       GString *gs = g_string_new (NULL);
       char buf[BUFSIZ];
 #if defined(_WIN32) || defined(__CYGWIN__)
-      setmode (fileno (stdin), _O_BINARY);
+      setmode (fileno (stdin), O_BINARY);
 #endif
       while (!feof (stdin)) {
 	size_t ret = fread (buf, 1, sizeof (buf), stdin);
@@ -672,7 +672,7 @@ output_options_t::get_file_handle (void)
     fp = fopen (output_file, "wb");
   else {
 #if defined(_WIN32) || defined(__CYGWIN__)
-    setmode (fileno (stdout), _O_BINARY);
+    setmode (fileno (stdout), O_BINARY);
 #endif
     fp = stdout;
   }