OpenGL2: Change normal/tangent vertex encoding.

code/renderergl2/glsl/pshadow_vp.glsl

@@ -11,5 +11,5 @@ void main()
 	gl_Position = u_ModelViewProjectionMatrix * vec4(attr_Position, 1.0);
 
 	var_Position  = attr_Position;
-	var_Normal    = attr_Normal * 2.0 - vec3(1.0);
+	var_Normal    = attr_Normal;
 }