fix safari syntax error - declare twice (#1851)

To avoid Safari bug, scope of for loop should enclose parent scope variables.


fixes #1753

lib/minify.js

@@ -57,6 +57,7 @@ function minify(files, options) {
                 keep_fnames: false,
                 properties: false,
                 reserved: [],
+                safari10: false,
                 toplevel: false,
             }, true);
         }