use no-safari10, not safari10 flag

bin/uglifyjs

@@ -35,7 +35,7 @@ program.option("--comments [filter]", "Preserve copyright comments in the output
 program.option("--config-file <file>", "Read minify() options from JSON file.");
 program.option("-d, --define <expr>[=value]", "Global definitions.", parse_js("define"));
 program.option("--ie8", "Support non-standard Internet Explorer 8.");
-program.option("--safari10", "Support Safari 10 by applying patch about For loop related scope issue. This flag is enabled by default.")
+program.option("--no-safari10", "Do not support Safari 10 by not applying patch about For loop related scope issue.")
 program.option("--keep-fnames", "Do not mangle/drop function names. Useful for code relying on Function.prototype.name.");
 program.option("--name-cache <file>", "File to hold mangled name mappings.");
 program.option("--self", "Build UglifyJS as a library (implies --wrap UglifyJS)");