Added missing includes in webgl.json. Fixes #2462.

Note: If extras need to be included too:
python build.py --include webgl --include extras --minify --output ../build/three-webgl-extras.min.js

utils/includes/webgl.json

 [
 	"../src/Three.js",
+	"../src/core/Clock.js",
 	"../src/core/Color.js",
 	"../src/core/Vector2.js",
 	"../src/core/Vector3.js",
@@ -27,6 +28,7 @@
 	"../src/lights/Light.js",
 	"../src/lights/AmbientLight.js",
 	"../src/lights/DirectionalLight.js",
+	"../src/lights/HemisphereLight.js",
 	"../src/lights/PointLight.js",
 	"../src/lights/SpotLight.js",
 	"../src/loaders/Loader.js",
@@ -47,6 +49,7 @@
 	"../src/materials/ParticleBasicMaterial.js",
 	"../src/materials/ShaderMaterial.js",
 	"../src/textures/Texture.js",
+	"../src/textures/CompressedTexture.js",
 	"../src/textures/DataTexture.js",
 	"../src/objects/Particle.js",
 	"../src/objects/ParticleSystem.js",
@@ -54,6 +57,7 @@
 	"../src/objects/Mesh.js",
 	"../src/objects/Bone.js",
 	"../src/objects/SkinnedMesh.js",
+	"../src/objects/MorphAnimMesh.js",
 	"../src/objects/Ribbon.js",
 	"../src/objects/LOD.js",
 	"../src/objects/Sprite.js",