title: superclass' methods not available
body: <p>Most docs on the init method of UI5 components mention to call the superclass' <code>init</code> method when overwriting it:</p>
  <pre class="lang-js prettyprint-override"><code>sap.ui.commons.Button.prototype.init.apply(this, arguments); 
  </code></pre>
  <p>But this is not working. When debugging <code>sap.ui.commonds.Button</code> and analyzing its prototype, there's <a href="https://github.com/SAP/openui5/blob/3d731d70a293f229f2992c7567cd4d3d997dd3a0/src/sap.ui.commons/src/sap/ui/commons/Button.js" rel="nofollow noreferrer">no <code>init</code> method present</a> - so of course <code>apply</code> fails.</p>
  <p>Am I doing anything wrong or is this a deprecated approach?</p>