Accept generics for defineProperty

Both `Object.defineProperty()` and `Object.defineProperties()` return their
first argument. Use a generic so that typings can be passed through.

src/lib/es5.d.ts

@@ -177,14 +177,14 @@ interface ObjectConstructor {
      * @param p The property name.
      * @param attributes Descriptor for the property. It can be for a data property or an accessor property.
      */
-    defineProperty(o: any, p: PropertyKey, attributes: PropertyDescriptor & ThisType<any>): any;
+    defineProperty<T>(o: T, p: PropertyKey, attributes: PropertyDescriptor & ThisType<any>): T;
 
     /**
      * Adds one or more properties to an object, and/or modifies attributes of existing properties.
      * @param o Object on which to add or modify the properties. This can be a native JavaScript object or a DOM object.
      * @param properties JavaScript object that contains one or more descriptor objects. Each descriptor object describes a data property or an accessor property.
      */
-    defineProperties(o: any, properties: PropertyDescriptorMap & ThisType<any>): any;
+    defineProperties<T>(o: T, properties: PropertyDescriptorMap & ThisType<any>): T;
 
     /**
      * Prevents the modification of attributes of existing properties, and prevents the addition of new properties.