Add missing goog.provide

The new version of the closure-compiler (version 20150729) wants that all the classes
tagged with `@constructor` to be provided (with `goog.provide`).

src/ol/webgl/shader.mustache

@@ -1,5 +1,8 @@
 // This file is automatically generated, do not edit
 goog.provide('{{namespace}}');
+goog.provide('{{namespace}}.Locations');
+goog.provide('{{className}}Fragment');
+goog.provide('{{className}}Vertex');
 
 goog.require('ol.webgl.shader');