Add Texture related constants to GLTFLoader

examples/js/loaders/GLTFLoader.js

@@ -463,6 +463,21 @@ THREE.GLTFLoader = ( function () {
 		10497: THREE.RepeatWrapping
 	};
 
+	var WEBGL_TEXTURE_FORMATS = {
+		6406: THREE.AlphaFormat,
+		6407: THREE.RGBFormat,
+		6408: THREE.RGBAFormat,
+		6409: THREE.LuminanceFormat,
+		6410: THREE.LuminanceAlphaFormat
+	};
+
+	var WEBGL_TEXTURE_TYPES = {
+		5121: THREE.UnsignedByteType,
+		32819: THREE.UnsignedShort4444Type,
+		32820: THREE.UnsignedShort5551Type,
+		33635: THREE.UnsignedShort565Type
+	};
+
 	var WEBGL_SIDES = {
 		1028: THREE.BackSide,  // Culling front
 		1029: THREE.FrontSide  // Culling back