fix again reserved props

lib/propmangle.js

@@ -149,6 +149,7 @@ function mangle_properties(ast, options) {
     }
 
     function should_mangle(name) {
+        if (reserved.indexOf(name) >= 0) return false;
         return cache.props.has(name)
             || names_to_mangle.indexOf(name) >= 0;
     }