Change docs and definition for shader input variable to Shader instead of Object

docs/api/en/materials/Material.html

@@ -295,7 +295,7 @@
 		These needs to be disposed by [page:Texture Texture].
 		</p>
 
-		<h3>[method:null onBeforeCompile]( [param:Object shader], [param:WebGLRenderer renderer] )</h3>
+		<h3>[method:null onBeforeCompile]( [param:Shader shader], [param:WebGLRenderer renderer] )</h3>
 		<p>
 		An optional callback that is executed immediately before the shader program is compiled.
 		This function is called with the shader source code as a parameter. Useful for the modification of built-in materials.

src/materials/Material.d.ts

 import { Plane } from './../math/Plane';
+import { Shader } from './../renderers/shaders/ShaderLib'
 import { EventDispatcher } from './../core/EventDispatcher';
 import { WebGLRenderer } from './../renderers/WebGLRenderer';
 import {
@@ -272,7 +273,7 @@ export class Material extends EventDispatcher {
    * @param shader Source code of the shader
    * @param renderer WebGLRenderer Context that is initializing the material
    */
-  onBeforeCompile ( shader : Object, renderer : WebGLRenderer ) : void;
+  onBeforeCompile ( shader : Shader, renderer : WebGLRenderer ) : void;
 
   /**
    * Sets the properties based on the values.