Fix a couple uses of ".prototype = new"

We don't want the THREE.Loader constructor to be executed, we just want
to setup our prototype chain. Using new would execute the constructor
logic of THREE.Loader.

examples/js/loaders/AWDLoader.js

@@ -116,8 +116,7 @@ THREE.AWDLoader = (function (){
   };
 
 
-  AWDLoader.prototype = new THREE.Loader();
-
+  AWDLoader.prototype = Object.create( THREE.Loader.prototype );
   AWDLoader.prototype.constructor = AWDLoader;
 
   AWDLoader.prototype.load = function ( url, callback ) {

examples/js/loaders/gltf/glTFLoader.js

@@ -16,7 +16,7 @@ THREE.glTFLoader = function (showStatus) {
     THREE.Loader.call( this, showStatus );
 }
 
-THREE.glTFLoader.prototype = new THREE.Loader();
+THREE.glTFLoader.prototype = Object.create( THREE.Loader.prototype );
 THREE.glTFLoader.prototype.constructor = THREE.glTFLoader;
 
 THREE.glTFLoader.prototype.load = function( url, callback ) {